### shape | gap | crack:

Volcano
* Follow the pace and rhtyhm of geologic movement and time.
* Learn about volcanoes from around the world.
* Many volcanoes are still active
  - form oceanic islands in the Pacific Ocean or Mediterranean Sea
* Many volcanoes have calderas
  - summit lakes through which heat and gases rise to the surface and escape
  - sit over magma chambers
* Most volcanoes are composite cones
  - explained by the collision or splitting apart of continental plates
* Most volcanoes are formed at plate boundaries
  - by the movement of tectonic plates on the surface of the earth
  - inactive most of the time, and thus are no warmer than non-volcanic mountains
  - stratovolcanoes
  - erupt for three to four weeks and then rest
* Most volcanoes have a volcanic crater at the top
  - craters
  - effects
  - negative effects
  - occur along the boundaries of the Earth's tectonic plates
* Most volcanoes occur at the plate boundaries
  - subduction zones and mid-oceanic ridges
  - near the edges of plates
  - provide various types of warnings before eruptions begin
  - reach a peak relatively early in their activity cycles and then gradually decline
  - therefore have both types of activity going on
* Shows the examples of earth's most dramatic agents of geologic change.
* Some volcanoes are active and tremors are frequent
  - calderas, which are pits formed by a collapsing lava chamber
  - individual mountains
  - more dangerous to humans than others because of the magma they erupt
* Some volcanoes can go hundreds, thousands, or even hundreds of thousands of years between eruptions
  - tens of thousands of years btween eruptions
  - coalsce to form a single island
  - destroy land, but others actually make new land
* Some volcanoes erupt all the time
  - for only a short time - a few days to weeks and never erupt again
  - form very quickly indeed
  - occur within a plate and are called intra-plate volcanoes
  - only erupt once and never again
  - produce fluid mudflows that do travel far down the volcano
  - show quite consistent patterns of activity while others are much more erratic
  - volcanos are gods and others are ancestors
* add mass to the continents when magma produces lava flows , tephra , and volcanic ash.
* affect humankind in many ways.
* affect the Earth in many ways
  - earth's climate in several ways
* also build up new islands and mountains and make the soil a good place for crops to grow.
* also create craters and calderas
  - mountains, produce new land, and enrich the soil with life-giving nutrients
  - form above hot spots, stationary upwellings of hot mantle rocks
  - give out gases such as carbon dioxide and sulphur dioxide
* also have a damaging effect on the weather
  - positive effect
  - make mineral deposits, like nickle and gold in Australia and Indonesia
  - produce huge landslides that can transform into lahars
* also release large amounts of water and carbon dioxide
  - particulates and gases into the atmosphere
* alternate active periods which can last for millions of years with long dormant phases.
* appear as bright spots on the smooth plains
  - thesmooth plains
* are a beautiful part of the earth, but they can also be very dangerous
  - natural way that the Earth and other planets have of cooling off
  - source of significant chemical energy, both as heat, and elements
  - threat to air safety from the moment that they erupt
* are also another way that hills are formed
  - at the center of a new paradigm shift in conceptions of how life began on Earth
  - common around the edge of the Pacific Ocean
  - hazards to man, animals and crops
  - more frequent along the plate boundaries
  - on the ocean bottom
  - part of the extended carbon cycle
  - responsible for some of the world's most fertile soils
  - an endogenous process
  - awesome manifestations of the fiery power contained deep within the Earth
  - both destructive and life-giving
  - composite hazards
  - considered one of the most destructive natural disasters of Earth
* are different from earthquakes
  - sizes and shapes
  - made when two tectonic plates come together
  - mountains with openings or vents that reach down in the Earth to where magma is found
  - nature's method of naturally refining and sorting minerals
  - necessary to sustain life but are devastating killers at the same time
* are one major geologic hazard that occurs in our world and Hawaii is one of their homex
  - of the most dramatic phenomena in nature
  - way Earth gives birth to itself
  - openings in the earth's crust that release molten rock
  - part of south parks
  - physical phenomenons
* are places where magma erupts as lava or ash
  - reaches the earth 's surface
  - puny builders of the earth's crust compared to their undersea buddies
  - still widespread and earthquakes are both frequent and severe
* are the exposure of magma at the Earth's surface, but sometimes magma remains underground
  - main way that the Earth releases heat
  - primary landforms built by repeated eruptions of lava and ash over time
  - unpredictable and highly dangerous
* are very dangerous because they are so powerful and filled with fire and gas
  - powerful, extremely destructive, and cause extensive damage
  - windows into how the Earth works
* arise from heating by magma at rifts, subduction zones, or hotspots.
* attest to the dynamic nature of the earth.
* begin to form when the rocks of the lower plate get pushed deep into the Earth.
* bring new supplies of minerals to the surface to enrich the land
  - up new material for land, erosion wears it down
* bury a village, and terrorism and torture reveal man's inhumanity to man.
* can affect the weather in a number of ways
  - also be a source of iridium
* can also form at a hot spot
  - hot spots as magma rises out of the sea floor
  - by other mechanisms besides subduction
  - islands near land or in the middle of lakes
  - have long-term effects on the climate, making the world cooler
  - make buildings catch fire
  - trigger tsunamis, floods, earthquakes, rockfalls, and mudflows
* can be dormant for hundreds of years
  - under water or on land
  - very dangerous and have killed many people in the last century
  - blanket square miles at a whack
* can cause many different problems
  - widespread destruction through several ways
* can change or modify weather systems
  - destroy an ecosystem by killing the plants, wildlife, and affect the weather
  - eject dust to it directly
  - erupt at any time, spitting out melted rock called lava
* can erupt for a very brief time or they can erupt many times over millions of years
  - long periods
  - in any type of season
  - explode at any time
  - form at a mid-ocean ridge
  - make larger changes all at once
* can occur on land or in the water
  - the Earth's moon
  - solitarily or in belts and chains
  - produce large quantities of particles and leave a record in the ice
  - put large amounts of dust particles high into the atmosphere
  - remain inactive, or dormant, for hundreds or thousands of years before erupting again
* come in a variety of sizes and types
  - all shapes and sizes
* commonly occur along colliding plate boundaries
  - repeat their past behavior
* constantly produce massive quantities of carbon dioxide.
* continue to happen today, throughout the world.
* contribute to the greenhouse effect.
* create islands for people to live on
  - new environments for plants and animals to migrate into
* deform constantly.
* differ widely in size and shape but three main types are recognized.
* do have an historical role well beyond their ancient mythology
  - produce chemicals which break down ozone
* dominate the landscape in parts of Central America.
* dot the lowland plain that spreads towards the ocean's blue swells.
* emit gases during eruptions
  - hot gases, ash and rock that are powerfully destructive
  - huge amounts of steam and hot water
  - large quantities of sulfur into the atmosphere
  - two sorts of ozone-depleting compounds
  - water vapor, carbon dioxide, and nitrogen, chiefly in the form of ammonia
* erupt after the bulk of the volcanic activity is actually over underground
  - and create the small area of land that joins North and South America
  - in a wide variety of ways
* erupt in different ways because of changes in temperature and gaseous content
  - under glaciers, causing apocalyptic floods as the ice melts instantaneously
* erupt, in part, because of pressure from dissolved gas
  - the crust quakes, and rivers rage
* expel streams of snow.
* explode and flowers grow tall
  - periodically and let out magma, ash, and gases
* fixes nitrogen into plant-available forms.
* form above the areas where the right conditions exist to melt rocks in the mantle
  - as magma rises from the melted slab
* form in Rocky Mountains
  - nine different stages
  - two places on the Earth
  - on the plate above the hot spot
* form where it passes over a hot spot carrying magma from deep below
  - rising magma breaks through the Earth's surface
* fume under the ice.
* generally occur along plate boundaries and are created when plates collide or move apart.
* generate their own weather which can be severe and different from that only a few km away.
* get progressively older away from permanent hotspot.
* give rise to numerous geologic and hydrologic hazards.
* grow because of repeated eruptions
  - by intrusion and extrusion
  - from their eruptions
  - with steam and ash from the lava about to spew over
* happen, mountains rise, and rocks wear down.
* have a wide range of impacts
  - an ecological impact that effects other indicators
  - similarity
* here consist mainly of Composite cones that emit volatile magma.
* impact all ecosystems and represent the most intense of nature's forces.
* inject large amounts of sulfur compounds, chlorine and water into the atmosphere.
* kills trees by toxic gasses.
* literally create new real estate, by building land above sea level.
* maintain the atmospheres of the Earth and Venus.
* make islands and add to the continents
  - up some of the biggest and most beautiful mountains in the world
* mark places where molten rock is rising to the surface of the Earth.
* occur at plate boundaries and also at hot spots
  - weak points in the Earth's crust
  - because the Earth's crust is broken into plates that resemble a jigsaw puzzle
  - in the mountains and deserts because it is hot and there lot of sand
  - most frequently at plate boundaries
  - under water as well as on land
  - when the mountains get too hot and they erupt
  - where the various moving plates which make up the Earth's surface meet
* often erupt at the same time as an earthquake
  - over hot spots
  - show signs that they are getting ready to erupt days to months in advance
  - wake in one of two moods
* play a role by sending up particles that block sunlight and cool the atmosphere.
* pose potential hazards to the surrounding populations.
* pour millions of tons of emanations into the atmosphere.
* produce a wide variety of hazards that can kill people and destroy property
  - natural hazards that can kill people and destroy property
  - steam, which forms clouds
  - volcanic rock
* provide a wealth of natural resources.
* pump massive quantities of gases, dust and ash into the atmosphere.
* release carbon dioxide, sulfur dioxide, and other gas molecules.
* renew the surface material and obliterate older surface features including craters.
* represent the magmatic arc.
* rise out of the clouds and the smell of sulfur is heavy in the air.
* rise, orgasm, and fall.
* sometimes erupt on the planet
  - occur above a hot spot
* spew noxious plumes of acidic gases.
* start at the edges of huge rocky plates that make up the earth's crust.
* usually destroy life
  - erupt through the top
  - lie along the subduction zone
+ Endogenous and exogenous: Earth sciences
  * Most volcanoes have a volcanic crater at the top. When they are active, materials pour out of it. This includes lava, steam, gaseous compounds of sulphur, ash and broken rock pieces.
+ Hotspot (geology), Discussion, Standard account of volcanic activity: Geology
  * Most volcanoes are explained by the collision or splitting apart of continental plates. This explains the long mountain ranges which have many volcanoes, such as the western edge of the Americas. It also explains the huge rift valleys such as the East African Rift Valley. Most Earth scientists accept that the cause of these great features is plate tectonics.
+ Volcanism, Aspects, Volcanoes: Volcanology
  * Volcanoes are places where magma reaches the earth's surface. The type of volcano depends on the location of the eruption and the consistency of the magma.
+ Volcano, How volcanoes are formed