Exploring the Valley of Ten Thousand Smokes - Katmai National Park & Preserve (U.S. National Park Service) Valley of Ten Thousand Smokes Exploring the Valley of Ten Thousand Smokes Steam rises from the Novarupta lava dome in 1918. Novarupta remains one of the many worthwhile destinations in the Valley of Ten Thousand Smokes. National Geographic Society Katmai expeditions photographs, Archives and Special Collections, Consortium Library, University of Alaska Anchorage. On June 6, 1912, a new volcano emerged on the Katmai landscape and forever altered this region. For 60 hours, a volcano later named Novarupta sent ash into the sky as high as 20 miles (30 km). Ash and pumice from the eruption also rushed down the Ukak River valley as pyroclastic flows and surges moving at more than 100 miles per hour (160 kilometers per hour). The Ukak River valley was transformed into 40 square miles (64 square kilometers) of barren ash. Heat trapped in the ash took decades to cool. Any water buried by the ash or that percolated into it flashed into steam.

The vents where the superheated steam emerged became the fumaroles that inspired the name Valley of Ten Thousand Smokes. Today the Valley of Ten Thousand Smokes (i.e. the Valley) offers a chance to explore a landscape created by the largest volcanic eruption of the 20th century. The beauty, scale, wildness, and mystery of the Valley make it one of the best places in the world to study the violence of volcanic eruptions and experience the raw power of nature. Destinations in the Valley of Ten Thousand Smokes The view from the Baked Mountain Huts is beautiful on sunny days, but they also provide shelter from the Valley's notoriously severe weather. NPS/M. Fitz Baked Mountain Huts Originally constructed in 1965 by the University of Alaska Geophysical Institute, the Baked Mountain Huts still offer a centralized location from which to explore the area. Two, small plywood huts provide protection from howling winds, blowing pumice, rain, and snow. Permits are not required, but a tent is always recommended in case you are unable to reach the huts or the huts are already full upon your arrival. However, huts should be shared by all who wish to stay in them.

A three-sided outhouse with a magnificent view of Mt. Griggs is also available at the Baked Mountain huts. The hike to the Baked Mountain huts is approximately twelve miles from the Valley Road and involves two river crossings, a bit of orienteering, and a final climb of about 800 feet (244 meters). If you choose to stay in the huts then pack out used toilet paper, garbage, and all food. Be aware that drinking water is normally not available at the huts after nearby snow fields melt in late spring and early summer. The National Park Service does not maintain the huts, so please do your part to leave the huts in good condition. Remember to latch all shutters and doors closed to prevent additional damage to these structures. Pack out all garbage and belongings from the huts upon your departure and do not leave any refuse or food behind. Most people entering the Valley do so by hiking along the base of the Buttress Range. NPS/M. Fitz Buttress Range The western side of the Valley is bordered by this ridge. Along the Buttress Range, several small, inset alcoves provide water and inviting places to camp.

Wildlife such as bears, ground squirrels, ptarmigan, and even caribou can be seen in this area. The crest of the Buttress Range is easily traversed along its length. Several warm springs seep from the base of the recent lava flows from Trident Volcano. NPS/M. Fitz Katmai Pass and the Southwest Trident Lava Flows Katmai Pass is one of the lowest points in the crest of the Aleutian Range in Katmai. It offers a relatively easy route between the Pacific Ocean and Bristol Bay watersheds. Until the 1912 eruption, a trail through Katmai Pass was frequently used by Alaska Natives as a trade route. While the historic trail through the pass was buried by ash and pumice, the area still provides many places to explore. Hikers moving south through the pass can explore the lava flows from southwest Trident and the warm springs that seep from underneath them. Hikers moving north through the pass can imagine what Robert Griggs saw in 1916 when he first gazed upon the steaming valley. The summit of Observation Mountain, several miles south of the pass, offers amazing views of the Katmai River gorge and valley.

The Knife Creek Glaciers plunge down from the summits of Mount Katmai and Trident Volcano. NPS/M. Fitz Knife Creek Glaciers and the Mount Katmai Caldera The lower slopes of the Knife Creek Glaciers are covered with as much as 6 feet (2 meters) of ash and pumice. Hikers can walk right up to the foot of and even on the glaciers, with caution. Three thousand feet above the glaciers lays the caldera of Mount Katmai. The summit of Mount Katmai collapsed during the 1912 Novarupta eruption leaving a caldera more than 2000 feet (600 m) deep. All routes to the caldera require crossing glaciers with crevasses. Reaching over 7500 feet in elevation, Mount Griggs is one of the tallest peaks in the Katmai region. NPS/M. Fitz Mount Griggs This is the tallest mountain bordering the Valley of Ten Thousand Smokes. Ascents of Mount Griggs can be made from its relatively gentle western slopes. The final approach to the summit requires a tricky traverse of glaciers and a snow and ice covered knife-edged ridge.

In late summer, water can be difficult to find near the base of Mount Griggs. Waterfalls and glacially carved lava flows border the Valley of Ten Thousand Smokes near the Mageik Lakes. NPS/M. Fitz Mageik Lakes When explorers first entered the Valley, they found the toe of two glaciers occupying the basin where two beautiful, but distinct lakes sit today. Surrounded by cascading waterfalls, a muddy, silt-laden lake can be found where the Buttress Range meets the slopes of Mount Mageik and Mount Martin. Closer to Katmai Pass, a turquoise colored lake can be found. The lava dome of Novarupta marks the center of a 1.5 mile (2 km) wide volcanic vent. NPS Novarupta It is a mere bump on the Valley’s floor and rises only 200 feet (65 meters) above its surface, but despite its small size this volcanic dome marks the vent of the largest volcanic eruption of the 20th century. When explorers first entered the Valley, this was one of the hottest areas and the dome still wafts warm steam.

Superheated jets of steam from nearby fumaroles cooked the surrounding ash and pumice and deposited kaleidoscopes of minerals. The area near Novarupta is the most colorful in the Valley. Novarupta is located approximately 14 miles from the Windy Creek trailhead on the Valley Road and about two miles one way from the Baked Mountain Huts. Water draining from perennial snowfields is typically available near Novarupta, even in late summer. River Crossings in the Valley of Ten Thousand Smokes You must approach river crossings in the Valley with caution. Rivers and streams are typically shallower and easier to cross at their widest margin. In flood conditions, deep gorges can be hidden (see inset). NPS The Valley of Ten Thousand Smokes poses special challenges for backcountry travelers. Suspended volcanic ash and glacially-derived sediments in rivers often make water depths impossible to estimate, and most of the rivers in the Valley are confined to narrow gorges that are deceptively deep and swift. Hikers must be especially cautious when choosing a place to cross the Valley’s rivers and creeks. The River Lethe and Knife Creek, for example, can only be forded in a few places.

If you cannot find a safe crossing, then you should not attempt to cross. You may also need to wait a day or longer until lower water levels permit safe crossing. Follow these tips when crossing: Watch the water’s surface and cross where you see small ripples, not waves. Cross early in the morning when runoff from glaciers is low. Release your pack’s belt buckle and loosen shoulder straps so you can drop your pack easily. Wear shoes while crossing. Allow yourself a retreat. Don’t commit to one route. Use a hiking pole or stick to help steady yourself and gauge the water’s depth. Novarupta - The Most Powerful Volcanic Eruption of the 20th Century Novarupta The Most Powerful Volcanic Eruption of the 20th Century June 6th, 1912 People in Juneau, Alaska, about 750 miles from the volcano, heard the sound of the blast – over one hour after it occurred. The morning of June 6th arrived on the Alaska peninsula to find the area which is now Katmai National Monument being shaken by numerous strong, shallow earthquakes.

The most powerful volcanic eruption of the 20th Century was about to begin � but very few people knew about it. The Alaska peninsula has a low population density today, but in 1912 it was even lower. Beyond the land shaken by the earthquake activity, the beginnings of this event were almost unnoticed. Volcanic Monitoring - 1912 vs. Today Today the stirring of an important volcano draws enormous global attention. Weeks or even months before most large eruptions, a buzz circulates through an electronically-connected community of volcano scientists as clusters of small earthquakes are detected by a global array of seismographs. Many scientists working at diverse global locations interpret this data and begin to collaborate about an awakening volcano and the eruption that might follow. Reports are posted on the internet and news stories communicate the volcano's activity to millions of people. Often it is a false alarm � the volcano is simply stirring. If the earthquakes strengthen and begin moving upwards, many of these scientists will travel to the area of potential eruption to make observations and set up a local network of data-gathering instruments.

However, in 1912, Alaska was not a US state, very few scientists were supported to do volcanic studies and a worldwide network of seismic monitoring was not in place. Scientists were just starting to understand the mechanics of volcanic eruptions. Novarupta Volcano Erupts! On June 6th, 1912 a tremendous blast sent a large cloud of ash skyward and the eruption of the century was underway. People in Juneau, Alaska, about 750 miles from the volcano, heard the sound of the blast � over one hour after it occurred. For the next 60 hours the eruption sent tall dark columns of tephra and gas high into the atmosphere. By the time the eruption ended the surrounding land was devastated and about 30 cubic kilometers of ejecta blanketed the entire region. This is more ejecta than all of the other historic Alaska eruptions combined. It was also thirty times more than the 1980 eruption of Mount St. Helens and three times more than the 1991 eruption of Mount Pinatubo, the second largest in the 20th Century.

Impact of the Eruption Forty years after the eruption, investigators finally realized that Novarupta - and not Katmai - was the source of the tremendous blast. The inhabitants of Kodiak, Alaska, on Kodiak Island, about 100 miles away, were among the first people to realize the severity of this eruption. The noise from the blast would have commanded their attention and the visual impact of seeing an ash cloud rise quickly to an elevation of 20 miles then drift towards them would have been terrifying. Within just a few hours after the eruption a thick blanket of ash began falling upon the town - and ash continued falling for the next three days, covering the town up to one foot deep. The residents of Kodiak were forced to take shelter indoors. Many buildings collapsed from the weight of heavy ash on their roofs. Outside, the ash made breathing difficult, stuck to moist eyes and completely blocked the light of the sun at midday. Any animal or person who was caught outside probably died from suffocation, blindness or an inability to find food and water. Pyroclastic Flow Back on the peninsula, heavy pyroclastic flows swept over 20 kilometers down the valley of Knife Creek and the upper Ukak River.

(A pyroclastic flow is a mixture of superheated gas, dust, and ash that is heavier than the surrounding air and flows down the flank of the volcano with great speed and force.) These flows completely filled the valley of Knife Creek with ash, converting it from a V-shaped valley into a broad flat plain. By the time the eruption was over, the world�s most extensive historic ignimbrite (solidified pyroclastic flow deposit) would be formed. It covered a surface area of over 120 square kilometers to depths of over 200 meters thick near its source. (The satellite image at right shows the original geographic extent of pyroclastic flow deposits as a yellow line.) Volcanic Ash Immediately after the June 6th blast, an ash cloud rose to an elevation of about 20 miles. It was then carried by the wind to the east, dropping ash as it moved. The ash deposits were thickest near the source of the eruption and decreased in thickness downwind. (The satellite image above/right has red contour lines showing the thickness of the ash deposits in the area of the eruption.

Measurable thickness of ash fell hundreds of miles beyond the one meter contour line.) When the eruption stopped on June 9th, the ash cloud had spread across southern Alaska, most of western Canada and several U.S. states. Winds then carried it across North America. It reached Africa on June 17th. Although the eruption had these far-reaching effects, most people outside of Alaska did not know that a volcano had erupted. More surprising is that no one knew for sure which of the many volcanoes on the Alaska peninsula was responsible. Most assumed that Mount Katmai had erupted but they were wrong. Valley of Ten Thousand Smokes After the eruption, the National Geographic Society began sending expeditions to Alaska to survey the results of the eruption and to inventory the volcanoes of the Alaskan peninsula. Robert Griggs led four of these expeditions. During his 1916 expedition, Griggs and three others traveled inland to the eruption area. What they found exceeded their imagination. First, the valley of Knife Creek was now barren, level and filled with a loose, sandy ash which was still hot at depth. Thousands of jets of steam were roaring from the ground.

Griggs was so impressed that he called it the �Valley of 10,000 Smokes�. James Hine, a zoologist on the expedition described the location: �Having reached the summit of Katmai Pass, the Valley of Ten Thousand Smokes spreads out before one with no part of the view obstructed. My first thought was: We have reached the modern inferno. I was horrified, and yet, curiosity to see all at close range captivated me. Although sure that at almost every step I would sink beneath the earth's crust into a chasm intensely hot, I pushed on as soon as I found myself safely over a particularly dangerous-appearing area. I didn't like it, and yet I did.� Katmai Caldera & Novarupta Dome Diamonds Don't Form From Coal During the eruption a large amount of magma was drained from magma chambers below. The result was a removal of support from beneath Mount Katmai which is six miles from Novarupta. The top several hundred feet of Katmai - about one cubic mile of material - collapsed into a magma chamber below. This collapse produced a crater about two miles in diameter and over 800 feet deep.

Early investigators assumed that Katmai was responsible for the eruption. This assumption was based upon Katmai being near the center of the impact area, Katmai was visibly reduced in height, and early witness accounts thought that the eruption cloud ascended from the Katmai area. Closer observation was not possible and expeditions into the impact zone would be very difficult to accomplish. The first scientific investigation to get an up-close look at the eruption area did not occur until 1916 when Robert Griggs found a 2-mile-wide caldera where Mount Katmai once stood. He also found a lava dome at the Novarupta vent. These observations convinced Griggs that Katmai was the source of the eruption. It was not until the 1950s - over forty years after the eruption - that investigators finally realized that ash and pyroclastic flow thicknesses were greatest in the Novarupta area. This discovery produced a revelation that Novarupta - and not Katmai - was the volcano responsible for the eruption (see satellite image medium resolution, 164 KB or higher resolution, 1330 KB ). This is possibly the most important false accusation in the history of volcanic study.

Could Novarupta Erupt Again? An eruption the size of Novarupta would ground commercial jet traffic across the North American continent. Other large eruptions on the Alaska peninsula are certain to happen in the future. Within the last 4000 years there have been at least seven Novarupta-scale eruptions within 500 miles of where Anchorage is located today. Future activity is expected because the Alaska peninsula is on an active convergent boundary. These large eruptions will have enormous local and global impact. Local impact will include the lahars, pyroclastic flows, lava flows and ash falls that are expected from a volcanic eruption. These can result in a significant loss of life and financial impact. The activity of these volcanoes is monitored by the United States Geological Survey and others so that eruptions can be predicted and their events mitigated. Large eruptions of Novarupta's scale at high latitudes can have a significant impact upon global climate. Recent studies have linked high latitude volcanic eruptions with altered surface temperature patterns and low rainfall levels in many parts of the world.

The 1912 eruption of Novarupta and other Alaskan volcano eruptions have been linked with drought and temperature changes in northern Africa. Another significant impact is the distribution of volcanic ash. The image at right shows the ash fall impact areas for five important volcanic eruptions of the 20th century. Augustine (1976), St. Helens (1980), Redoubt (1990) and Spurr (1992) all produced ash falls of significant regional impact. However, Novarupta's ash fall was far greater than any other Alaska eruption in recorded history and contained a greater volume than all of the Alaska eruptions which have been recorded combined. One of the most important reasons to monitor volcanic eruptions is the potential danger that they present to commercial air traffic. Jet engines process enormous amounts of air and flying through finely dispersed ash can cause engine failure. Impacting the tiny ash particles at high speed is very similar to sandblasting. This can "frost" the jet's windshield and damage external parts of the plane. Before the danger of flying through finely dispersed ash was appreciated several commercial jets were forced to land after sustaining serious damage while in the air.

Eruptions the size of Spurr, Augustine, Redoubt and St. Helens can damage jets flying over 1000 miles away. An eruption the size of Novarupta would ground commercial jet traffic across the North American continent. What Can We Do About It? People can not prevent this type of eruption. They can assess the potential impact, develop with the possibility of loss in mind, plan a response, educate the public and key decision makers, and monitor the region where it might occur. The more you know about a natural hazard, the greater your chances of avoiding injury or loss. We are lucky to have this record of the past. This pristine preserve is famous for true wilderness adventures, including exceptional bear viewing History In 1912 Novarupta Volcano on the Alaska Peninsula violently erupted and rocked the area now known as Katmai National Park and Preserve. The wilderness was turned into a dynamic landscape of smoking valleys, ash-covered mountains and small holes and cracks fuming with steam and gas. Only one other eruption in historic times, on the Greek island of Santorini in 1500 BC, displaced more ash and pumice.

Four years later explorer Robert Grigg climbed Katmai Pass and became the first person to see the valley floor with its thousands of steam vents. He named it the Valley of 10,000 Smokes and led the effort that turned Katmai into a national monument. In 1980 the monument was enlarged to 4.2 million acres and designated a national park and preserve. Katmai National Monument was established in 1918, but so few people visited the remote area that no rangers were stationed here until 1950. Today, Katmai National Park and Preserve remains a wilderness landscape with little development. Ecosystem and Wildlife The fumaroles no longer smoke and hiss and today the park is best known for its brown bear population that tops more than 2,000. At the peak of the bear viewing season in July, throngs of visitors arrive at Brooks River to watch bears snagging salmon in mid-air just 30 yards away. Katmai is also home to the Alagnak Wild River and several large lakes.

Naknek Lake is the largest and support all five species of Pacific salmon as well as rainbow trout, Arctic char, Arctic grayling and northern pike, making the park a famed destination for sport anglers. Activities Most people come to Katmai via floatplane. For many visitors, this is the first time in a small aircraft. Others arrive for the opportunity to raft, hike the Valley of 10,000 Smokes, camp in the backcountry or kayak the chain of lakes and rivers known as the Savonoski Loop. Unconnected to any town by roads, Katmai requires additional planning, costs and advance reservations for extended visits. Bear viewing tour packages to the park, even one-day tours, can be arranged from Kodiak, Homer and Anchorage. Enabled Facilities Brooks Camp, the park's summer headquarters on the shores of Naknek Lake, 35 miles from King Salmon, is the hub of activity at Katmai and its most developed area. The camp features a lodge and restaurant, a campground, a store, kayak rentals and Brooks Camp Visitor Center (907-481-1781). Float planes from King Salmon load and unload passengers right along the shore at Brooks Camp.

A trail and floating bridge leads to the most popular attractions in the park; a series of three bear viewing platforms overlooking the Brooks River. The last deck, at Brook Falls, is the prime viewing area, where visitors can photograph the salmon making spectacular leaps and a 900-pound brown bear at the top of the cascade waiting with open jaws to catch it. Thanks to an incredible sockeye salmon run, in July there might be a dozen bears here with two or three of them atop the falls. Departing from Brooks Camp is the only road in Katmai. The 23-miles dirt road winds past wildlife-inhabited meadows and river valleys and ends at Three Forks Overlook, which has a sweeping view of the Valley of 10,000 Smokes. A park concessionaire runs a daily bus tour to Three Forks Overlook and back, stopping along the way to pick up hikers and backpackers who use it to reach the backcountry.Scattered throughout the park and on the outside coast are a number of fly-in lodges that offer all-exclusive package trips. Many of them cater to sport anglers and include boats for traveling on the large lakes and up rivers. Some are designed exclusively for bear viewing.

Fees There are no entrance fees in Katmai nor are permits required to enter the backcountry. There is a nightly per-person fee for Brooks Camp Campground. Reservations for both camping and day use must be made prior to any visit to Katmai through the National Recreation Reservation Service (877-444-6777, 518-885-3639; ). Accessibility The park is open year-round but the concessioner services at Brooks Camp, the main access point for the park, is offered only June through mid-September. King Salmon can be reached by commercial airline from Anchorage while Brooks Camp, 30 air miles away, is only accessible by small floatplane. Bear viewing tour packages to the park, even one-day tours, can be arranged from Kodiak, Homer and Anchorage. The best source of information is the Katmai National Park Headquarters (907-246-3305; ) located in King Salmon. At the King Salmon airport terminal and open year-round is the King Salmon Visitor Center (907-246-4250). Either the park headquarters or the visitor center can provide a list of all Katmai's commercial operators.

Take your itinerary with you using our My Alaska Trip feature and the TravelAlaska app. × If you would like to compare where services are located, you can Add to My Alaska to compile a list and see all the points on the same map. Katmai National Park and Preserve– Map It Katmai National Park and Preserve– Map It Katmai National Park and Preserve– Map It Katmai National Park and Preserve– Map It Katmai National Park and Preserve– Map It Katmai National Park and Preserve– Map It Brooks Lodge Alaska (Brooks Falls) Bear Viewing Tour; Katmai NP Wilderness Lodges Tour Overview This Alaska tour at Brooks Lodge focuses on the experience of staying inside Katmai National Park and the natural wonders this area has to offer. Brooks Falls and Brooks Lodge are world renowned for their incredible brown bear viewing as well as the Valley of 10,000 Smokes. Alaska’s bears are attracted to this area in Alaska specifically during the time of the Brooks River salmon run (typically July and September). These bears actually don’t inhabit this area year round, only arriving to feed on salmon a couple of times a year.

The Katmai National Monument was established in 1918 to protect the valleys created by the major 1912 volcanic eruption of Novarupta , which formed the Valley of Ten Thousand Smokes in the region surrounding Mount Katmai. Katmai protects 9,000 years of human history as well as important habitat for salmon and the thousands of brown bears that feed on them. The Brooks Camp and Lodge area is the gateway to the Valley of 10,000 Smokes and even though this volcano is no longer active, it is still an impressive sight and worth a visit! Food and meals: Visitors are not allowed to bring food to Brooks. This is for the protection of both people and bears. A dining area in the main lodge serves breakfast, lunch and dinner buffets daily. Meals are not included with any of the packages. The lodge only accepts cash, Visa and MasterCard. What's Included 2 Brooks Lodge to Anchorage Today you have the opportunity to participate in the guided tour to Valley of 10,000 Smokes (not included).

The tour departs Brooks at 8:30am and the 23 mile drive to the valley offers scenic views and you possibly may see wildlife. At the valley you will have amazing views from the Overlook Cabin and informative displays of the area's history. Those interested may hike down with the tour guide to examine the ash and pumice "Valley" floor. The hike is a bit strenuous. You return to Brooks Camp in the afternoon. If flying back to Anchorage today, you will depart upon return to Brooks. Flight back to Anchorage is via King Salmon or Kulik. ** ** The return to Anchorage can vary and depends on the length of stay and availability of flights. If you book the 2 day/1 night program you typically return to Anchorage at approximately 9:00 pm. With the 3 day/2 night or 4 day/3 night programs you typically depart Anchorage around 9:30 am on day 1, and return to Anchorage at approximately 4:00 pm on the last day. A night in Anchorage before and after this tour is required.

Accommodations at Brooks Lodge: Rooms are very simple; all have 2 sets of bunk beds (4 single beds total), a sink, toilet (not fully enclosed), shower and heater. Television, internet and cell phone service are not available at Brooks Camp. Air Flight Information: The flight from Anchorage to King Salmon/Kulik is in a twin-engine, wheeled plane. The flight from King Salmon/Kulik to Brooks is on a small, 6 to 8 passenger, single-engine float plane. Due to limited space, visitors are asked to keep their luggage to a minimum and bring only soft-side luggage. Please do not bring hard-side suitcases! Frequently Asked Questions - Katmai National Park & Preserve (U.S. National Park Service) Frequently Asked Questions 1. Where is Katmai? Katmai National Park & Preserve ( click here for a park map ) is located on the northern Alaska Peninsula, northwest of Kodiak Island and southwest of Homer, Alaska. The park’s headquarters is in King Salmon, about 290 air miles southwest of Anchorage. 2. How do I get to Katmai? Can you drive to King Salmon or Brooks Camp from Anchorage?

Unlike most national parks in the United States, Katmai is almost exclusively accessed by plane or boat. You can not drive to Katmai, Brooks Camp, or King Salmon from Anchorage, Alaska. Most destinations in Katmai National Park & Preserve are directly accessed via air taxi flights from Anchorage, Dillingham, Homer, King Salmon, Kodiak, and other nearby Alaska towns and villages. Regularly scheduled commercial flights to King Salmon (AKN) are available from Ted Stevens Anchorage International Airport (ANC) via PenAir and Alaska Airlines . Boats can access the Pacific coast of Katmai. Brooks Camp and other locations along the Naknek River drainage can be reached by power boat from the villages of Naknek and King Salmon. Please see Katmai’s Directions page for more information. 4. How do I get names of Katmai's air taxis, bear guides, and other commercial operators? Go to the NPS Alaska Region's commercial services webpage and there you will find a link for commercial visitor services within Katmai National Park and Preserve. That list will contain the names and contact information for air taxis, bear watching guides, and other authorized commercial services. 5. How do I get to the Pacific coast of Katmai? What can I do there?

Most people who visit the Pacific side of Katmai arrive via a chartered airplane from Anchorage, Homer, Kodiak and other nearby towns, cities, and villages. Private and chartered boats can also access many places on the coast as well. The Pacific coast of Katmai offers a combination of amazing scenery, wilderness, and wildlife viewing opportunities. Most people who visit this area of the park go to watch bears, but there are many opportunities for sport fishing and wilderness trekking too. Go to the NPS Alaska Region's commercial services webpage for an updated list of authorized commerical visitor services. No. Backcountry areas do not have fees or facilities. No backcountry permits are required. Please visit the backcountry hiking and camping pages for more information. Brooks Camp 7. How do I get to Brooks Camp? Most people who visit Brooks Camp fly from Anchorage to King Salmon on a commercial airline ( Alaska Airlines or PenAir ) and fly from King Salmon to Brooks Camp on KatmaiAir. KatmaiAir offers seat fares for trip to Brooks Camp. For current fares and to make a reservation visit Katmailand.com . 8. Where do you see bears once you're at Brooks Camp? In July and September, bears are everywhere at Brooks Camp.

They can be found walking trails, fishing in the river, and even napping on the beach. During July, many bears can be seen fishing at Brooks Falls which is about 1.2 miles (1.9 km) from the Brooks Camp Visitor Center. In September, most bears are seen at the mouth of the Brooks River. Please note that in June and August few bears, if any, can be seen at Brooks Camp. Please download the brochure, Bear Viewing at Brooks Camp , for more information. 9. Where are the wildlife viewing platforms and is there a time limit for viewing? In the park, there are three viewing platforms located in Brooks Camp along the south side of Brooks River. The Falls Platform is located immediately adjacent to Brooks Falls, the Riffles Platform is located about 100 yards (91 m) downstream of Brooks Falls, and the Lower River Platform at the mouth of the Brooks River near Brooks Lodge. The Falls Platform has a limited capacity of 40 people. When the Falls Platform is at maximum capacity, rangers maintain a waiting list and anyone on the platform is limited to one hour at a time on the Falls Platform. This system helps to provide equal access to the Falls Platform during peak days of visitation.

If you visit Brooks Camp in July, expect crowded conditions at Brooks Falls. Volcanoes of the United States [USGS] Introduction Few natural forces are as spectacular and threatening, or have played such a dominant role in shaping the face of the Earth, as erupting volcanoes. Volcanism has built some of the world's greatest mountain ranges, covered vast regions with lava (molten rock at the Earth's surface), and triggered explosive eruptions whose size and power are nearly impossible for us to imagine today. Fortunately, such calamitous eruptions occur infrequently. Of the 50 or so volcanoes that erupt every year, however, a few severely disrupt human activities. Between 1980 and 1990, volcanic activity killed at least 26,000 people and forced nearly 450,000 to flee from their homes. Though few people in the United States may actually experience an erupting volcano, the evidence for earlier volcanism is preserved in many rocks of North America. Features seen in volcanic rocks only hours old are also present in ancient volcanic rocks, both at the surface and buried beneath younger deposits.

A thick ash deposit sandwiched between layers of sandstone in Nebraska, the massive granite peaks of the Sierra Nevada mountain range, and a variety of volcanic layers found in eastern Maine are but a few of the striking clues of past volcanism. With this perspective, an erupting volcano is not only an exciting and awesome spectacle in its own right but a window into a natural process that has happened over and over again throughout Earth's history. The Earth's crust, on which we live and depend, is in large part the product of millions of once-active volcanoes and tremendous volumes of magma (molten rock below ground) that did not erupt but instead cooled below the surface. Such persistent and widespread volcanism has resulted in many valuable natural resources throughout the world. For example, volcanic ash blown over thousands of square kilometers of land increases soil fertility for forests and agriculture by adding nutrients and acting as a mulch. Groundwater heated by large, still-hot magma bodies can be tapped for geothermal energy. And over many thousands of years, heated groundwater has concentrated valuable minerals, including copper, tin, gold, and silver, into deposits that are mined throughout the world.

The United States ranks third, behind Indonesia and Japan, in the number of historically active volcanoes (that is, those for which we have written accounts of eruptions). In addition, about 10 percent of the more than 1,500 volcanoes that have erupted in the past 10,000 years are located in the United States. Most of these volcanoes are found in the Aleutian Islands, the Alaska Peninsula, the Hawaiian Islands, and the Cascade Range of the Pacific Northwest; the remainder are widely distributed in the western part of the Nation. A few U.S. volcanoes have produced some of the largest and most dangerous types of eruptions in this century, while several others have threatened to erupt. Scientists at the U.S. Geological Survey (USGS) engage in a variety of research activities in order to reduce the loss of life and property that can result from volcanic eruptions and to minimize the social and economic turmoil that can result when volcanoes threaten to erupt. These activities include studies of the physical processes before, during, and after a volcanic eruption, assessments of volcano hazards, and public outreach to translate scientific information about volcanoes into terms that are meaningful to the public and public officials.

Monitoring volcanoes for signs of activity, another vital component, is carried out by USGS earth scientists at three volcano observatories, which were established to study active volcanoes in Hawaii (1912), the Cascades (1980), and Alaska (1988). These researchers record earthquakes, survey the surfaces of volcanoes, map volcanic rock deposits, and analyze the chemistry of volcanic gas and fresh lava to detect warning signs of impending activity and determine the most likely type of activity that will affect areas around a volcano. During the past 10 years, several warnings of eruptions were issued by the USGS and monitoring of recently active volcanoes in the United States was expanded. Predicting the time and size of volcanic eruptions, however, remains a difficult challenge for scientists. Volcanoes and the Theory of Plate Tectonics Volcanoes are not randomly distributed over the Earth's surface. Most are concentrated on the edges of continents, along island chains, or beneath the sea forming long mountain ranges.

More than half of the world's active volcanoes above sea level encircle the Pacific Ocean to form the circum-Pacific "Ring of Fire." In the past 25 years, scientists have developed a theory--called plate tectonics--that explains the locations of volcanoes and their relationship to other large-scale geologic features. According to this theory, the Earth's surface is made up of a patchwork of about a dozen large plates that move relative to one another at speeds from less than one centimeter to about ten centimeters per year (about the speed at which fingernails grow). These rigid plates, whose average thickness is about 80 kilometers, are spreading apart, sliding past each other, or colliding with each other in slow motion on top of the Earth's hot, pliable interior. Volcanoes tend to form where plates collide or spread apart, but they can also grow in the middle of a plate, as for example the Hawaiian volcanoes. Hawaiian volcanoes Few places on Earth allow closer or more dramatic views of volcanic activity than Mauna Loa and Kilauea volcanoes on the island of Hawaii. Their frequent but usually nonexplosive eruptions make them ideal for scientific study.

Kilauea's eruptions are so intensely monitored that scientists have assembled a detailed picture of the volcano's magma reservoir "plumbing" system and how it behaves before and during eruptions. Studies of these volcanoes and the surrounding ocean floor continue to improve our understanding of the geologic history of the Hawaiian Island chain and the ability of scientists to determine volcanic hazards that threaten island residents. Eruptions of Hawaiian volcanoes are typically non-explosive because of the composition of the magma. Almost all of the magma erupted from Hawaii's volcanoes forms dark gray to black volcanic rock (called basalt), generally in the form of lava flows and, less commonly, as fragmented lava such as volcanic bombs, cinders, pumice, and ash. Basalt magma is more fluid than the other types of magma (andesite, dacite, and rhyolite). Consequently, expanding volcanic gases can escape from basalt relatively easily and can propel lava high into the air, forming brilliant fountains sometimes called "curtains of fire." Lava, whether erupted in high fountains or quietly pouring out, collects to form flows that spread across the ground in thin broad sheets or in narrow streams.

The fluid nature of basalt magma allows it to travel great distances from the vent (the place where lava breaks ground) and tends to build volcanoes in the shape of an inverted warrior shield, with slopes less than about 10 degrees. Volcanoes with this kind of profile are called shield volcanoes. Hawaiian volcanoes erupt at their summit calderas and from their flanks along linear rift zones that extend from the calderas. Calderas are large steep-walled depressions that form when a volcano's summit region collapses, usually after a large eruption empties or partly empties a reservoir of magma beneath the volcano. Rift zones are areas of weakness within a volcano that extend from the surface to depths of several kilometers. Magma that erupts from the flank of a volcano must first flow underground through one of the volcano's rift zones, sometimes traveling more than 30 kilometers from the summit magma reservoir before breaking the surface. Mauna Loa. Rising more than 9,000 meters from the seafloor, Mauna Loa is one of the world's largest active volcanoes; from its base below sea level to its summit, Mauna Loa is taller than Mount Everest.

It has erupted 15 times since 1900, with eruptions lasting from less than 1 day to as many as 145 days. The most recent eruption began before dawn on March 25, 1984. Brilliant lava fountains lit the night-time sky as fissures opened across the floor of the caldera. Within hours, the summit activity stopped and lava began erupting from a series of vents along the northeast rift zone. When the eruption stopped 3 weeks later, lava flows were only 6.5 kilometers from buildings in the city of Hilo. Mauna Loa erupts less frequently than Kilauea, but it produces a much greater volume of lava over a shorter period of time. Kilauea Volcano. Kilauea's longest rift-zone eruption in historical time began on January 3, 1983. A row of lava fountains broke out from its east rift zone about 17 kilometers from the summit caldera; within a few months, the activity settled down to a single vent.

Powerful fountaining episodes hurled molten rock 450 meters into the air and built a cone of lava fragments that quickly became the tallest landmark on the rift zone. The eruption changed style abruptly in July 1986 when lava broke out through a new vent. Instead of regular episodes of high lava fountaining, lava spilled continuously onto Kilauea's surface. The steady outpouring of lava formed a lake of molten rock that became perched atop a small shield volcano. By June 1991, the shield was about 60 meters tall and 1,600 meters in diameter, and lava from the eruption had covered 75 square kilometers of forest and grassland, added 120 hectares of new land to the island, and destroyed 179 homes. Although most of Kilauea's historical rift eruptions were much briefer, prolonged eruptive activity in the east rift zone from 1969 to 1974 formed a similar shield, Mauna Ulu (Hawaiian for "Growing Mountain"), and an extensive lava field on the volcano's south flank.

The geologic record shows that such large-volume eruptions from the rift zones and the summit area, covering large parts of Kilauea's surface, have occurred many times in the recent past. In fact, about 90 percent of Kilauea's surface is covered with lava flows that are less than 1,100 years old. Most eruptions at Kilauea can be viewed at close range, but a few historical eruptions were dangerously explosive. Fast-moving mixtures of ash and gas, called pyroclastic surges, raced across the summit area and into the southwest rift zone during an eruption in 1790. Footprints preserved in a layer of ash 30 kilometers southwest of the summit probably include those of a party of Hawaiian warriors and their families who were crossing the volcano when the eruption struck. An estimated 80 of the 250 people were killed by suffocating clouds associated with the pyroclastic surges. A smaller explosive eruption in 1924 from Halemaumau Crater in Kilauea summit caldera, which killed a photographer who was too close, hurled rocks weighing as much as 8 tons as far as 1 kilometer.

Cascade volcanoes Volcanoes of the Cascade Range erupt far less frequently than Kilauea and Mauna Loa, but they are more dangerous because of their violently explosive behavior and their proximity to populated and cultivated areas in Washington, Oregon, and California. The 1980 eruption of Mount St. Helens in southwest Washington dramatically illustrated the type of volcanic activity and destruction these volcanoes can produce. Scientific studies of the eruption of Mount St. Helens and the eruptive histories of other Cascade volcanoes continue to improve public awareness and understanding of these potentially dangerous peaks. In contrast to Kilauea, Cascade volcanoes erupt a variety of magma types that generate a wide range of eruptive behavior and build steepsided cones known as composite volcanoes. In addition to basalt, andesite and dacite magmas are common. These magmas are so highly viscous, or sticky, that expanding volcanic gases cannot easily escape from them. This causes a tremendous build-up in pressure, often leading to extremely explosive eruptions. During such eruptions, magma is shattered into tiny fragments (chiefly ash and pumice) and ejected thousands of meters into the atmosphere or even the stratosphere.

Under the force of gravity, sometimes these fragments sweep down a volcano's flanks at speeds of more than 100 kilometers per hour, mixing with air and volcanic gases to form pyroclastic flows. Rock fragments can also mix with water in river valleys to form lahars (volcanic debris flows and mudflows) that destroy everything in their paths. Andesite and dacite magmas also erupt to form lava flows. Because these lavas are more viscous ("stickier") than basalt, they tend to form thicker flows that travel shorter distances from the vent; consequently, andesite and dacite lavas typically build tall cones with steep slopes of more than 20 degrees. Mount Baker, Washington. Eyewitness reports of small ashy plumes and active steam vents on Mount Baker dating as far back as the mid-1800's were clear evidence that the ice-covered volcano had one of the most active geothermal systems among Cascade volcanoes. When new fumaroles and unusually dark vapor plumes appeared abruptly in March 1975, however, people in the Northwest became concerned about an impending eruption and possible avalanches and lahars from Sherman Crater, a vent just south of Mount Baker's summit.

Despite a tenfold increase in the release of heat by the volcano during the next 12 months, which resulted in extensive changes to the ice cover in Sherman Crater and produced minor releases of ash, no eruption occurred. The thermal activity was not accompanied by earthquakes, which generally precede most eruptions, and since 1976, the volcano has not showed additional signs of activity. The increased thermal activity between 1975 and 1976 prompted public officials and Puget Power to temporarily close public access to the popular Baker Lake recreation area and to lower the reservoir's water level by 10 meters. Significant avalanches of debris from the Sherman Crater area could have swept directly into the reservoir, triggering a disastrous wave that would have caused loss of life and damage to the reservoir. Mount Rainier, Washington. Mount Rainier has not produced a significant eruption in the past 500 years, but scientists consider it to be one of the most hazardous volcanoes in the Cascades. Mount Rainier has 26 glaciers containing more than five times as much snow and ice as all the other Cascade volcanoes combined.

If only a small part of this ice were melted by volcanic activity, it would yield enough water to trigger enormous lahars. Mount Rainier's potential for generating destructive mudflows is enhanced by its great height above surrounding valleys and its "soft" interior. The volcano stands about 3,000 meters above river valleys leading from its base. Volcanic heat and ground water have turned some of the volcano's originally hard lava into soft clay minerals, thereby weakening its internal structure. These conditions make Mount Rainier extremely susceptible to large landslides. Several have occurred in the past few thousand years, one as recently as about 600 years ago. These landslides, apparently containing great volumes of water, quickly turned into lahars as they rushed down river valleys. Mount St. Helens, Washington. The catastrophic eruption on May 18, 1980, was preceded by 2 months of intense activity that included more than 10,000 earthquakes, hundreds of small phreatic (steam-blast) explosions, and the outward growth of the volcano's entire north flank by more than 80 meters.

A magnitude 5.1 earthquake struck beneath the volcano at 08:32 on May 18, setting in motion the devastating eruption. Within seconds of the earthquake, the volcano's bulging north flank slid away in the largest landslide in recorded history, triggering a destructive, lethal lateral blast of hot gas, steam, and rock debris that swept across the landscape as fast as 1,100 kilometers per hour. Temperatures within the blast reached as high as 300 degrees Celsius. Snow and ice on the volcano melted, forming torrents of water and rock debris that swept down river valleys leading from the volcano. Within minutes, a massive plume of ash thrust 19 kilometers into the sky, where the prevailing wind carried about 490 tons of ash across 57,000 square kilometers of the Western United States. The well-documented landslide at Mount St. Helens has helped geologists to recognize more than 200 similar deposits at other volcanoes in the world, including several other Cascade peaks. Geologists now realize that large landslides from volcanoes are far more common than previously thought--seventeen such volcanic landslides have occurred worldwide in the past 400 years.

Consequently, when scientists evaluate the types of volcanic activity that may endanger people, giant landslides are now included, in addition to other types of volcanic activity such as lava flows, pyroclastic flows, lahars, and falling ash. Following the 1980 explosive eruption, more than a dozen extrusions of thick, pasty lava built a mound-shaped lava dome in the new crater. The dome is about 1,100 meters in diameter and 250 meters tall. Lassen Peak, California. Long before the recent activity of Mount St. Helens, a series of spectacular eruptions from Lassen Peak between 1914 and 1917 demonstrated the explosive potential of Cascade volcanoes. Small phreatic explosions began on May 30, 1914, and were followed during the next 12 months by more than 150 explosions that sent clouds of ash as high as 3 kilometers above the peak. The activity changed character in May 1915, when a lava flow was observed in the summit crater. A deep red glow from the hot lava was visible at night 34 kilometers away.

On May 19, an avalanche of hot rocks from the lava spilled onto snow and triggered a lahar that extended more than 15 kilometers from the volcano. The most destructive explosion occurred on May 21, when a pyroclastic flow devastated forests as far as 6.5 kilometers northeast of the summit and lahars swept down several valleys radiating from the volcano. An enormous ash plume rose more than 9 kilometers above the peak, and the prevailing winds scattered the ash across Nevada as far as 500 kilometers to the east. Lassen Peak continued to produce smaller eruptions until about the middle of 1917. Alaskan volcanoes The Alaska Peninsula and the Aleutian Islands have about 80 major volcanic centers that consist of one or more volcanoes. Recent violent eruptions have demonstrated that volcanic hazards do exist in some areas of Alaska, even though it is sparsely populated. Alaskan volcanoes have produced one or two eruptions per year since 1900.

At least 20 catastrophic caldera-forming eruptions have occurred in the past 10,000 years; the awesome eruption of 1912 at Novarupta in the Katmai National Monument is the most recent. Scientists are particularly concerned about the volcanoes whose eruptions can affect the Cook Inlet region, where 60 percent of Alaska's population lives. Redoubt Volcano. Redoubt Volcano erupted for the fourth time this century on December 14, 1989. Following several days of strong explosive activity, a series of lava domes grew in Redoubt's summit crater during the next four months. Most of the domes were destroyed by explosions or collapsed down the volcano's north flank. Some of these events triggered small pyroclastic flows that melted snow and ice on the volcano to form lahars in Drift River Valley, which empties into Cook Inlet 35 kilometers away. Ash produced by the eruptions severely affected air traffic enroute to Anchorage, Alaska's largest city and a major hub of domestic and international commercial air traffic. Many domestic carriers suspended service to Alaska following major explosive events, and several international carriers temporarily rerouted flights around Alaska.

On December 15, a jetliner enroute to Japan encountered an ash cloud while descending into Anchorage. The plane quickly lost power in all four engines and lost 4,000 meters in altitude before the pilots were able to restart the engines. The aircraft landed safely in Anchorage, but it sustained more than $80 million in damage. Lahars generated during the eruption threatened an oil-storage facility located on the banks of Drift River. Oil is pumped from more than a dozen wells in Cook Inlet to the facility and then loaded onto tankers, which dock just offshore. A lahar on January 2 flooded part of the facility with nearly a meter of water, forcing its shutdown until workers could restore power. This and subsequent lahars prompted the Cook Inlet Pipeline Company to temporarily halt oil production from some oil wells and reduce the amount of oil stored at the facility between tanker loadings. Augustine Volcano. One of the most active volcanoes in Cook Inlet is Augustine, whose symmetrical cone rises 1,254 meters above the sea.

Since Captain James Cook discovered and named it in 1778, Augustine has erupted in 1812, 1883, 1935, 1963-64, 1976, and 1986. Curiously, the quiet intervals between these eruptions apparently have shortened from 70 to 10 years. Augustine's 1986 eruption was similar to the pattern of events observed in 1976. After eight months of earthquake activity beneath the volcano, a violent explosion began on March 26. Billowing ash plumes rose more than 10 kilometers above the vent, pyroclastic flows sped down the volcano's flanks into the sea, and ash spread throughout Cook Inlet. A second stage began April 23, when lava began erupting near the volcano's summit and added about 25 meters to the top of the existing lava dome. Small pyroclastic flows accompanied growth of the dome. Scientists were worried that this eruption might trigger a giant landslide from Augustine's steep upper cone, which could enter the sea to create a tsunami (powerful seismic sea wave).

At least 12 landslides are known to have occurred at Augustine. The most recent slide took place at the onset of the 1883 eruption when a part of the volcano's summit collapsed into the sea. Within one hour, a tsunami as high as 9 meters crashed ashore on the coast of the Kenai Peninsula 80 kilometers away. No one was killed and property damage was only minor because the tsunami hit at low tide. Subsequent eruptions have rebuilt a steep cone of overlapping lava domes similar to the cone that existed just before the 1883 landslide. Novarupta, Katmai National Monument. The largest eruption in the world this century occurred in 1912 at Novarupta on the Alaska Peninsula. An estimated 15 cubic kilometers of magma was explosively erupted during 60 hours beginning on June 6-- about 30 times the volume erupted by Mount St. Helens in 1980! The expulsion of such a large volume of magma excavated a funnel-shaped vent 2 kilometers wide and triggered the collapse of Mount Katmai volcano 10 kilometers away to form a summit caldera 600 meters deep and about 3 kilometers across.

Extrusion of the lava dome, called Novarupta, near the center of the 1912 vent marked the end of the eruption. Little was known about the spectacular effects of this great eruption until 1916, when a scientific expedition sponsored by the National Geographic Society visited the area. To their amazement, they found a broad valley northwest of Novarupta marked by a flat plain of loose, "sandy" ash material from which thousands of jets of steam were hissing. The eruption had produced pyroclastic flows that swept about 21 kilometers down the upper Ukak River valley. The thickness of the resulting pumice and ash deposits in the upper valley is not known but may be as great as 200 meters. In 1916, the deposits were still hot enough to boil water and form countless steaming fumaroles; hence the expedition named this part of the Ukak River the "Valley of Ten Thousand Smokes." Trident Volcano.

Eruptions of andesitic lava flows between 1953 and 1960 built a new cone on Trident's southwest flank, adding yet another to the volcano's older complex of three overlapping cones (hence the name Trident). A huge cloud of rising ash was seen on February 15, 1953, in the direction of Katmai National Monument; 3 days later clear weather permitted U.S. Navy pilots to spot a blocky lava flow emerging from Trident's southwest flank. Slow extrusion of lava during the next 4 months built an irregularly shaped lava dome about 1.5 kilometers long and 600 meters tall. Trident continued to erupt intermittently through 1960, generating three lava flows as long as 4.5 kilometers from the same vent and numerous ash-producing explosive eruptions. Mount Veniaminof. Mount Veniaminof is a massive composite volcano with a summit caldera about 8 kilometers in diameter. Since its formation about 3,700 years ago, the caldera has filled with ice to a depth of at least 60 meters.

Between June 1983 and January 1984, a series of small explosions, lava fountains, and lava flows erupted from a small cinder cone within the caldera. The explosions hurled molten lava from the cinder cone, and lava flows melted a pit about 1.5 kilometers in diameter in the ice near the base of the volcano. Water from the melting ice formed a temporary lake. Mount Spurr. The summit cone of Mount Spurr consists of a large lava dome built in the center of a horseshoe-shaped crater formed earlier by a large landslide. At the southern edge of this ancient crater is a younger, more active cone known as Crater Peak. Scientists have determined that Crater Peak is the source for at least 35 ash layers found in the Cook Inlet area, all of which were erupted in the past 6,000 years. Until recently, a warm turquoise-colored lake partially filled its crater. A series of explosive eruptions from Crater Peak on June 27, 1992, generated ash plumes as high as about 14 kilometers, small pyroclastic flows that swept down the south and east sides of the cone, and small lahars.

The reawakening of Crater Peak followed nearly a year of increased earthquake activity, which escalated further on June 26, less than 1 day before its first eruption. Not all of the explosive episodes were preceded by a change in seismicity beneath the volcano, a condition that required scientists to maintain a 24-hour watch for extended periods of time in order to issue sudden reports and warnings of eruptive activity. The west side of Cook Inlet received a light to moderate ashfall during the largest explosive episode on August 18; Anchorage was blanketed with about 3 millimeters of ash, causing the Anchorage International Airport to close for a few hours. During an eruption at night on September 17, a spectacular display of lightning and incandescent ballistics and pyroclastic flows were witnessed by hunters who camped about 18 kilometers to the southeast; a faint glow above Crater Peak was also visible from as far away as Anchorage. Restless calderas The largest and most explosive volcanic eruptions eject tens to hundreds of cubic kilometers of magma onto the Earth's surface.

When such a large volume of magma is removed from beneath a volcano, the ground subsides or collapses into the emptied space, to form a huge depression called a caldera. Some calderas are more than 25 kilometers in diameter and several kilometers deep. Calderas are among the most spectacular and active volcanic features on Earth. Earthquakes, ground cracks, uplift or subsidence of the ground, and thermal activity such as hot springs, geysers, and boiling mud pots are common at many calderas. Such activity is caused by complex interactions among magma stored beneath a caldera, ground water, and the regional buildup of stress in the large plates of the Earth's crust. Significant changes in the level of activity at some calderas are common; these new activity levels can be intermittent, lasting for months to years, or persistent over decades to centuries. Although most caldera unrest does not lead to an eruption, the possibility of violent explosive eruptions warrants detailed scientific study and monitoring of some active calderas. Recently, scientists have recognized volcanic unrest at two calderas in the United States, Long Valley Caldera in eastern California and Yellowstone Caldera in Yellowstone National Park, Wyoming.

Whether unrest at these calderas simply punctuates long periods of quiet or is the early warning sign of future eruptions is an important but still unanswered question. Long Valley Caldera, California. Long Valley Caldera lies on the eastern front of the Sierra Nevada, about 300 kilometers east of San Francisco. A huge explosive eruption about 700,000 years ago formed the caldera and produced pyroclastic flows that traveled 65 kilometers from the vent and covered an area of about 1,500 square kilometers. Ash from the caldera-forming eruption fell as far east as Nebraska. Within the past 40,000 years, eruptions have been restricted to a linear zone of vents, including the Mono-Inyo Craters Volcanic Chain, that extends about 50 kilometers north from the northwest part of the caldera. This volcanic chain consists of many vents that have erupted in the past several thousand years. Eruptions from vents as recently as 550 years ago produced lava flows, pyroclastic flows, and ash, all of rhyolitic composition.

Geologic mapping shows that some eruptions were preceded by ground cracking, suggesting that the ground was pulled apart or stretched as magma neared the surface. Three moderate earthquakes south of the caldera and one beneath the caldera on May 25-26, 1980, marked the beginning of unrest that continues into the 1990's. Swarms of earthquakes beneath the caldera, changes in several hot springs, and the formation of new springs have occurred since 1980. Precise surveys have also shown that the central part of the caldera has risen by more than 50 centimeters since 1975. This unrest is probably related to the stretching (east-west extension) of the Earth's crust that is known to be occurring in the region around the caldera, and it probably also involves the rise of magma beneath the caldera. Scientists do not know if this unrest will lead to volcanic activity, but the geologically recent eruptions along the Mono-Inyo Craters Volcanic Chain suggest that future eruptions are possible. Yellowstone Caldera, Yellowstone National Park, Wyoming. Yellowstone Caldera is one of the largest and most active calderas in the world.

The spectacular geysers, boiling hot springs, and mud pots that have made Yellowstone famous--and even the strikingly beautiful Grand Canyon of Yellowstone through which the Yellowstone River plunges--owe their existence to the tremendous volcanic forces that have affected the region during the past 2 million years. Cataclysmic eruptions 2.0, 1.3, and 0.6 million years ago ejected huge volumes of rhyolite magma; each eruption formed a caldera and extensive layers of thick pyroclastic-flow deposits. The youngest caldera is an elliptical depression, nearly 80 kilometers long and 50 kilometers wide, that occupies much of Yellowstone National Park. The caldera is buried by several extensive rhyolite lava flows erupted between 75,000 and 150,000 years ago. The Earth's crust beneath Yellowstone National Park is still restless. Precise surveys have detected an area in the center of the caldera that rose by as much as 86 centimeters between 1923 and 1984 and then subsided slightly between 1985 and 1989.

Scientists do not know the cause of these ups and downs but hypothesize that they are related to the addition or withdrawal of magma beneath the caldera, or to the changing pressure of the hot ground water system above Yellowstone's large magma reservoir. Also, Yellowstone National Park and the area immediately west of the Park are historically among the most seismically active areas in the Rocky Mountains. Small-magnitude earthquakes are common beneath the entire caldera, but most are located along the Hebgen Lake fault zone that extends into the northwest part of the caldera. A magnitude 7.5 earthquake occurred along this zone in 1959. Active Volcanoes: Windows into the Past Molten rock has erupted onto the surface of the Earth throughout its 4.5-billion-year history. Although many of these ancient rocks were removed by erosion, volcanic deposits can be found beneath younger rocks in many parts of the United States. To a geologist, such long-lasting volcanic rocks look like those formed by today's active volcanoes. Many ancient volcanic rocks, however, change somewhat with time, as they become firmly consolidated, buried by younger deposits, and sometimes folded and faulted by the continuous shifting of the Earth's crust.

Even minerals of volcanic rocks may change, if after burial they encounter high pressures and temperatures. Most active volcanoes are built on older volcanic deposits erupted from ancient volcanoes, and visitors to the present-day volcanoes walk or drive across these products of past volcanism. For example, anyone driving across the Cascade Range, sunbathing at Waikiki, or fishing on the Alaska Peninsula is there because old volcanic rocks form the landscape. One step further back in time from today's active volcanoes are people who picnic in the White Mountains of New Hampshire, enjoy the autumn colors in the Blue Ridge of Shenandoah National Park, and hike in the rugged Big Bend National Park of Texas. Many of the rocks in these areas were formed by eruptions or by intrusion of magma into the Earth's crust many millions of years ago. Because volcanic activity has been so important in shaping the Earth, watching active volcanoes today provides a window through which we can glimpse and reconstruct the early volcanic history of our planet. As we increase our knowledge about volcanic processes, by studying volcanoes erupting today as well as those that have lain dormant for hundreds to thousands of years, we increase our ability to predict when and how volcanoes will erupt.

Accurate predictions, presented in terms that are meaningful to public officials, will minimize the number of lives lost and the social and economic upheaval that an eruption can cause. Glossary Andesite A volcanic rock containing 53-63% silica with a moderate viscosity when in a molten state. Ash Fragments less than 2 millimeters in diameter of lava or rock blasted into the air by volcanic explosions. Basalt A volcanic rock consisting of less than 53% silica with a low viscosity when in a molten state. Caldera A large volcanic depression, commonly circular or elliptical when seen from above. Composite volcano A steep-sided volcano composed of many layers of volcanic rocks, usually of high-viscosity lava and fragmented debris such as lahar and pyroclastic deposits. Dacite A volcanic rock containing 63-68% silica with a high viscosity when in a molten state. Dome A steep-sided mound that forms when viscous lava piles up near a volcanic vent. Domes are formed by andesite, dacite, and rhyolite lavas. Fumarole A vent that releases volcanic gases, including water vapor (steam).

Lahar A flowing mixture of water and rock debris that forms on the slopes of a volcano, sometimes referred to as debris flow or mudflow. The term comes from Indonesia. Lava Molten rock that erupts from a vent or fissure; see magma. Magma Molten rock that contains dissolved gas and crystals, formed deep within the Earth. When magma reaches the surface, it is called lava. Phreatic eruption A type of volcanic explosion that occurs when water comes in contact with hot rocks or ash near a volcanic vent, causing steam explosions. Pumice A light-colored volcanic rock containing abundant trapped gas bubbles formed by the explosive eruption of magma. Because of its numerous gas bubbles, pumice commonly floats on water. Pyroclastic flow A hot, fast-moving and high-density mixture of ash, pumice, rock fragments, and gas formed during explosive eruptions. Pyroclastic surge Same process as pyroclastic flow but of much lower density. Rhyolite A volcanic rock containing more than 68% silica with a very high viscosity when in a molten state. Shield volcano A volcano shaped like an inverted warrior's shield with long gentle slopes produced by eruptions of low-viscosity basaltic lava.

Silica The molecule formed of silicon and oxygen (SiO2) that is the basic building block of volcanic rocks and the most important factor controlling the fluidity of magma. The higher a magma's silica content, the greater its viscosity or "stickiness." Vent The opening at the Earth's surface through which volcanic materials (magma and gas) escape. Volcano A vent in the surface of the Earth through which magma erupts and also the landform that is constructed by the erupted material. Volcanic landslide The downslope movement of soil, rock debris, and sometimes glacial ice, with or without water, from the flank of a volcano. The metric units used in this publication can be converted to English units by using the approximate conversions given below: Length Further Reading Decker, Robert, and Decker, Barbara, 1989, Volcanoes: San Francisco, Freeman, 285 p. (An information-packed introduction to the study of volcanoes written in an easy-to-read style.) Editors, 1982, Volcano: in the series Planet Earth, Alexandria, Virginia, Time-Life Books,176 p.

(A well illustrated and readable general survey of volcanoes and their activity.) McClelland, Lindsay, Simkin, Tom, Summers, Marjorie, Nielsen, Elizabeth, and Stein, T.C., editors, 1989, Global Volcanism 1975-1985: Englewood Cliffs, New Jersey, Prentice-Hall, 656 p. (A full account of volcanism on Earth based on eyewitness accounts from geologists and other scientists, reporters, travelers, and other keen observers.) Simkin, Tom, Seibert, Lee, McClelland, Lindsay, Bridge, David, Newhall, Christopher, and Latter, J.H., 1981, Volcanoes of the World: Stroudsburg, Pa., Hutchinson Ross, 233 p. (A comprehensive regional directory of worldwide volcanic activity during the past 10,000 years; activity presented in table format.) Tilling, R.l., 1982, Volcanoes: Reston, Virginia, U.S. Geological Survey general-interest publication, 46 p.

(A general introduction for the nonspecialist to the study of volcanoes, with focus on the nature, types, workings, products, and hazards of volcanoes.) Tilling, R.l., 1984, Eruptions of Mount St. Helens: Past, present, and future: Reston, Virginia, U.S. Geological Survey general-interest publication, 46 p. (A nontechnical summary, illustrated by many color photographs and diagrams, of the abundant scientific data available for the volcano, with emphasis on the catastrophic eruption on May 18, 1980, which caused the worst volcanic disaster in U.S. history.) Tilling, R.l., 1987, Eruptions of Hawaiian volcanoes: Past, present, and future: Reston, Virginia, U.S. Geological Survey general-interest publication, 54 p.

(A nontechnical summary, illustrated by color photographs and drawings, of the eruption history, style, and products of two of Hawaii's active volcanoes, Kilauea and Mauna Loa.) Wood, C.A., and Kienle, Jurgen, editors, 1990, Volcanoes of North America--United States and Canada: Cambridge University Press, 354 p. (A rich compilation of volcanoes and volcanic fields in North America that were formed in the past 5 million years; includes more than 250 entries prepared by leading experts in volcanology.) This publication is one of a series of general interest publications prepared by the U.S. Geological Survey to provide information about the earth sciences, natural resources, and the environment. To obtain a catalog of additional titles in the series "General Interest Publications of the U.S. Geological Survey," write: U.S. Geological Survey

Question: In which US state can you find the area named "The Valley of the 10,000 Smokes"?
Answer: ALASKA