remiconnesson/oceanservice-noaa-facts huggingface dataset:
# What is the highest point on Earth as measured from Earth's center?

##### **What does this have to do with the OCEAN service?**

_The [National Geodetic Survey](https://geodesy.noaa.gov/) (part of the National Ocean Service) measures and monitors our [ever-changing planet](/facts/geodesy.html) by mapping its gravity field and determining the precise location of points on Earth’s surface. Measurements of the Earth contribute to a wide range of important activities, including mapping and charting, navigation, flood risk determination, transportation, land use, and ecosystem management._

Mount Everest, located in Nepal and Tibet, is usually said to be the highest mountain on Earth. Reaching **8,848 meters**[![29,029 feet](/bs4/img/question.svg)](#) at its summit, Everest is indeed the highest point above global mean sea level—the average level for the ocean surface from which elevations are measured. But the summit of Mt. Everest is not the farthest point from Earth’s _center_.

Earth is not a perfect [sphere](/facts/earth-round.html), but is a bit thicker at the Equator due to the centrifugal force created by the planet’s constant rotation. Because of this, the highest point above Earth’s center is the peak of Ecuador’s Mount Chimborazo, located just one degree south of the Equator where Earth’s bulge is greatest. The summit of Chimborazo is **6,268 meters** [![20,564 feet](/bs4/img/question.svg)](#) above sea level. However, due to the Earth’s bulge, the summit of Chimborazo is over **2,072 meters** [![6,800  feet](/bs4/img/question.svg)](#) farther from the center of the Earth than Everest’s peak. That makes Chimborazo the closest point on Earth to the stars.  

You may be surprised to learn that Everest is not the tallest mountain on Earth, either. That honor belongs to Mauna Kea, a volcano on the Big Island of Hawaii. Mauna Kea originates deep beneath the Pacific Ocean, and rises more than **10,210 meters** [![33,500  feet](/bs4/img/question.svg)](#) from base to peak.
# What are High Seas Forecasts?

[![map of high seas forecast areas](/facts/highseas.jpg "The National Weather Service provides High Seas text and graphic forecasts for large areas of the  Atlantic and Pacific oceans, U.S. coastal areas, and the Great Lakes.")](https://www.nws.noaa.gov/om/marine/zone/hsmz.htm)

[](https://www.nws.noaa.gov/om/marine/zone/hsmz.htm)

[_NOAA's_](https://www.nws.noaa.gov/om/marine/zone/hsmz.htm) _[High Seas Forecasts](https://www.weather.gov/marine/hsmz) are marine weather forecasts prepared for mariners and transmitted around the world in real- and near-real-time. Note: the above map i_

Seafaring can be very dangerous for ships at sea. For centuries, little could be done to make shipping safer, due to the unpredictability of the weather, the vast size of the ocean, and a lack of international cooperation in the open ocean. However, the 1912 sinking of the "unsinkable" _Titanic_, with more than 1,500 casualties, sparked global concern about safety and standards for ships at sea. This tragedy would lead to new international conventions that established safety requirements and provided more accurate and standardized weather forecasts.

Today, [National Meteorological and Hydrological Services](https://public.wmo.int/en/our-mandate/how-we-do-it/role-and-operation-of-nmhss) around the world provide real- or near-real-time weather forecasts and data that are transmitted globally. The World Meteorological Organization’s (WMO) [Global Observing System](https://public.wmo.int/en) relies on member countries, which use their facilities on land, at sea, and in space via satellites to forecast weather conditions. Together, these resources allow meteorological and other environmental observations on a global scale.

As a member of WMO, NOAA's [National Weather Service](https://www.weather.gov/) (NWS) provides [High Seas Forecasts](https://www.weather.gov/marine/hsmz) for large areas of the U.S. Atlantic and Pacific oceans. The NWS also provides marine forecasts for [U.S. coastal areas and the Great Lakes](https://www.weather.gov/marine/usamz), [offshore waters](https://www.weather.gov/marine/wrdoffmz), and part of the Arctic Ocean. The NWS’s [Unified Surface Analysis](https://ocean.weather.gov/unified_analysis.php) of world weather also provides data on a complex set of surface observations. These forecasts from NOAA, as well as predictions from other National Meteorological and Hydrological Services around the world, are available to anyone, and, most importantly, to all ships at sea.
# What is Seaspeak?

## Seaspeak is the official language of navigators the world over.

![NOAA Corps Ensign Diane Perry on the NOAA Ship Thomas Jefferson](/facts/seaspeak.jpg "NOAA Corps Ensign Diane Perry on the NOAA Ship Thomas Jefferson")

Whether on the high seas or at port, misunderstood communication can lead to serious and even dangerous situations. "Seaspeak", the official language of the seas, helps to prevent miscommunication.

Have you ever wondered how crews on ships at sea communicate? Nowadays, crews consist of men and women from all over the world, and often, a single ship's crew comes from a number of different countries. But that was not always the case. Back in the 1960s, the United States and the United Kingdom dominated ocean traffic, and 80 percent of ships' crews were native English speakers. By the end of 1970s, however, the situation had reversed, and today, 80 percent of ship's crews do not speak English as a first language.

So what happens when a ship captain needs to communicate with his or her crew, to another ship, or to shore? Whether on the high seas or at port, misunderstood communication can lead to serious and even dangerous situations.

To avoid such confusion, in 1983 a group of linguists and shipping experts created a new system of communication called Seaspeak. English was chosen as the principle lexicon for Seaspeak because it was the most common language spoken on ships at that time, and, importantly, it was also the language of civil aviation. In 1988, the [International Maritime Organization](https://www.imo.org/) made Seaspeak the official language of the seas.

Seaspeak defines the rules of how to talk on a ship's radio. The number of words is limited to ensure that messages and conversations are short and clear. Eight words, called message markers, precede each sentence. These words are Advice, Answer, Information, Instruction, Intention, Question, Request, and Warning.

An important rule of Seaspeak is that numbers made up of two or more digits are spoken in single digits. For example, the number 33 is spoken as "three three" and the time 9:33 a.m. is spoken as "zero nine three three." [Coordinated Universal Time](http://www.nhc.noaa.gov/aboututc.shtml)—the primary time standard or international time scale by which the world regulates clocks and time—is always used at sea.

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Seaspeak Example

Here's an example of Seaspeak between the captains of two vessels that plan to rendezvous at a predetermined buoy:

"Question: What is your estimated time of arrival at buoy number six two? Over."

"Answer: Estimated time of arrival at buoy number six two is zero nine three zero. Out."

![](/bootstrap/img/shadow1.png)

**Last updated:** 06/16/24  
**Author:** NOAA  
[How to cite this article](/about/faq.html)

[Contact Us](/contact.html)
# What is subsidence?

![geodetic mark](/facts/subsidence.jpg "geodetic mark")

_This geodetic mark in Louisiana is anchored deep below the ground and was level with the ground when it was originally placed there, but now the ground around the mark has subsided._

Subsidence - sinking of the ground because of underground material movement—is most often caused by the removal of water, oil, natural gas, or mineral resources out of the ground by pumping, fracking, or mining activities.

Subsidence can also be caused by natural events such as earthquakes, soil compaction, [glacial isostatic adjustment](/facts/glacial-adjustment.html), erosion, sinkhole formation, and adding water to fine soils deposited by wind (a natural process known as loess deposits). Subsidence can happen over very large areas like whole states or provinces, or very small areas like the corner of your yard. In the Chesapeake Bay area, for example, land subsidence may be caused by a combination of sediment loading (when rivers deposit sediment in an area that then sinks under the additional weight) and sediment compaction after groundwater is removed.

One way to measure these changes is through the Global Positioning System (GPS). NOAA’s National Geodetic Survey maintains a national network of high-precision GPS receivers, called a Continuously Operating Reference Station (CORS), that can be used to track height changes at the station. Areas without a CORS can measure subsidence from satellite InSAR (Interferometric Synthetic Aperture Radar), temporary GPS receivers, repeated surveys of geodetic [leveling](https://www.ngs.noaa.gov/heightmod/Leveling/), or installations of ground and water sensors.

Did you know? - *More than 80 percent of the identified subsidence in the U.S. is a consequence of our exploitation of underground water.*

- [National Geodetic Survey](https://geodesy.noaa.gov/)

- [Variations in Sea Level](https://geodesy.noaa.gov/GRD/GPS/Projects/CB/SEALEVEL/sealevel.html)

- [U.S. Geological Survey](https://www.usgs.gov/special-topic/water-science-school/science/land-subsidence?qt-science_center_objects=0#qt-science_center_objects)

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# What are the Horse Latitudes?

## The horse latitudes are subtropical regions known for calm winds and little precipitation.

![horse latitudes](/facts/horselatitudes.jpg "short caption")

The horse latitudes are regions located at about 30 degrees north and south of the equator. These latitudes are characterized by calm winds and little precipitation.

The horse latitudes are located at about 30 degrees north and south of the equator. It is common in this region of the subtropics for winds to diverge and either flow toward the poles (known as the prevailing westerlies) or toward the equator (known as the trade winds). These diverging winds are the result of an area of high pressure, which is characterized by calm winds, sunny skies, and little or no precipitation.

According to legend, the term comes from ships sailing to the New World that would often become stalled for days or even weeks when they encountered areas of high pressure and calm winds. Many of these ships carried horses to the Americas as part of their cargo. Unable to sail and resupply due to lack of wind, crews often ran out of drinking water. To conserve scarce water, sailors on these ships would sometimes throw the horses they were transporting overboard. Thus, the phrase 'horse latitudes' was born.

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The northern and southern Horse Latitudes are sometimes referred to as the "calms of Cancer" and the '"calms of Capricorn," respectively.

![](/bootstrap/img/shadow1.png)

**Last updated:** 06/16/24  
**Author:** NOAA  
[How to cite this article](/about/faq.html)

[Contact Us](/contact.html)

Did you know? - 

- The northern and southern Horse Latitudes are sometimes referred to as the "calms of Cancer" and the '"calms of Capricorn," respectively.
# Why do we name tropical storms and hurricanes?

![hurricane Ike](/facts/storm-names.jpg "Hurricane Sandy as seen from NOAA's GOES-13 satellite on October 28, 2012. NOAA's National Ocean Service helps coastal communities prepare for and recover from major coastal storms such as hurricanes. ")

_NOAA's [GOES East](https://www.nesdis.noaa.gov/current-satellite-missions/currently-flying/geostationary-satellites) satellite captured this view of Hurricane Florence shortly after the storm made landfall near Wrightsville Beach, N.C. on Friday, Sept. 14, 2018._

Until the early 1950s, tropical storms and hurricanes were tracked by year and the order in which they occurred during that year. Over time, it was learned that the use of short, easily remembered names in written as well as spoken communications is quicker and reduces confusion when two or more tropical storms occur at the same time. In the past, confusion and false rumors resulted when storm advisories broadcast from radio stations were mistaken for warnings concerning an entirely different storm located hundreds of miles away.

In 1953, the United States began using female names for storms and, by 1978, both male and female names were used to identify Northern Pacific storms. This was then adopted in 1979 for storms in the Atlantic basin.

NOAA’s National Hurricane Center does not control the naming of tropical storms. Instead, there is a strict procedure established by the World Meteorological Organization. For Atlantic hurricanes, there is a list of male and female names which are used on a six-year rotation. The only time that there is a change is if a storm is so deadly or costly that the future use of its name on a different storm would be inappropriate. In the event that more than twenty-one named tropical cyclones occur in a season, [a supplemental list of names](https://public.wmo.int/en/media/press-release/wmo-hurricane-committee-retires-tropical-cyclone-names-and-ends-use-of-greek) are used.

For a complete list of upcoming and retired storm names, visit the [National Weather Service website](https://www.nhc.noaa.gov/aboutnames_history.shtml).
# What is a Plimsoll line?

![photo of Plimsoll mark on the hull of a floating ship](/facts/plimsoll-line.jpg)

_Plimsoll mark on the hull of a floating ship._

The Plimsoll line is a reference mark located on a ship’s hull that indicates the maximum depth to which the vessel may be safely immersed when loaded with cargo. This depth varies with a ship’s dimensions, type of cargo, time of year, and the water densities encountered in port and at sea. Once these factors have been accounted for, a ship’s captain can determine the appropriate Plimsoll line needed for the voyage (see above image):

-   I**TF** = Tropical Fresh Water
-   **T** = Tropical
-   **F** = Fresh Water
-   **S** = Summer
-   **W** = Winter
-   **WNA** = Winter North Atlantic
-   **AB** = Letters indicating the registration authority (American Bureau of Shipping in the image shown; the circle with the line through it indicates whether or not the cargo is loaded evenly)

Samuel Plimsoll (1824–1898) was a member of the British Parliament who was concerned with the loss of ships and crews due to vessel overloading. In 1876, he persuaded Parliament to pass the Unseaworthy Ships Bill, which mandated marking a ship's sides with a line that would disappear below the waterline if the ship was overloaded. The line, also known as the Plimsoll mark, is found midship on both the port and starboard hulls of cargo vessels and is still used worldwide by the shipping industry.
# What is a geographic information system?

##### **Did you know?**

_Each year, we celebrate GIS Day in November as part of Geography Awareness Week. GIS Day started in 1999 as an educational event for GIS users to showcase their projects that have real-world applications. Opening their doors to schools, businesses, and the public, GIS users and vendors demonstrate the benefits of GIS and how it makes a difference in our society. Today, GIS Day is recognized globally with events occurring in dozens of countries._

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Did you know? - *Each year, we celebrate GIS Day in November as part of Geography Awareness Week. GIS Day started in 1999 as an educational event for GIS users to showcase their projects that have real-world applications. Opening their doors to schools, businesses, and the public, GIS users and vendors demonstrate the benefits of GIS and how it makes a difference in our society. Today, GIS Day is recognized globally with events occurring in dozens of countries.*

- [GIS Day](http://gisday.com/)

- [Geography Awareness Week](http://www.geographyawarenessweek.org)

- [NOAA Digital Coast](https://www.coast.noaa.gov/digitalcoast/)

- [Office of Coast Survey](https://www.nauticalcharts.noaa.gov)

- [Office of Response & Restoration](https://response.restoration.noaa.gov/resources/maps-and-spatial-data)

- [National Centers for Coastal Ocean Science](https://coastalscience.noaa.gov)

-
# What is Tectonic Shift?

![Map of tectonic plates from National Park Service; source: http://www.nature.nps.gov/geology/education/education_graphics.cfm (Modified by NPS from: R. J. Lillie. 2005. Parks and Plates.)](/facts/tectonics.jpg)

_The Earth is made up of roughly a dozen major plates and several minor plates._

##### **Did you know?**

_Measuring the motion of tectonic plates is part of the science of geodesy. To define the shape of the Earth, NOAA’s National Geodetic Survey, part of the National Ocean Service, uses a variety of techniques to measure the planet’s rate of rotation, its plate motion, and the ways that gravity affects certain scientific processes. Learn more: [What is Geodesy?](/facts/geodesy.html)_

The Earth is in a constant state of change. Earth’s crust, called the lithosphere, consists of 15 to 20 moving tectonic plates. The plates can be thought of like pieces of a cracked shell that rest on the hot, molten rock of Earth’s mantle and fit snugly against one another. The heat from radioactive processes within the planet’s interior causes the plates to move, sometimes toward and sometimes away from each other. This movement is called plate motion, or tectonic shift.

Our planet looks very different from the way it did 250 million years ago, when there was only one continent, called _Pangaea,_ and one ocean, called _Panthalassa._ As Earth’s mantle heated and cooled over many millennia, the outer crust broke up and commenced the plate motion that continues today.

The huge continent eventually broke apart, creating new and ever-changing land masses and oceans. Have you ever noticed how the east coast of South America looks like it would fit neatly into the west coast of Africa? That’s because it did, millions of years before tectonic shift separated the two great continents.

Earth’s land masses move toward and away from each other at an average rate of about 1.5 centimeters (0.6 inches) a year. That’s about the rate that human toenails grow! Some regions, such as coastal California, move quite fast in geological terms — almost 5 centimeters (two inches) a year — relative to the more stable interior of the continental United States. At the “seams” where tectonic plates come in contact, the crustal rocks may grind violently against each other, causing earthquakes and volcano eruptions. The relatively fast movement of the tectonic plates under California explains the frequent earthquakes that occur there.

Did you know? - *Measuring the motion of tectonic plates is part of the science of geodesy. To define the shape of the Earth, NOAA’s National Geodetic Survey, part of the National Ocean Service, uses a variety of techniques to measure the planet’s rate of rotation, its plate motion, and the ways that gravity affects certain scientific processes. Learn more: [What is Geodesy?](https://oceanservice.noaa.gov/facts/geodesy.html)*
# What is geocaching?

## Geocaching is an **outdoor treasure-hunting activity** that uses GPS-enabled devices.

![](/facts/geocaching.jpg)

In geocaching, participants navigate to a specific set of GPS coordinates and then attempt to find the "geocache," (usually a container or marker) at that location. The survey mark shown here illustrates how some caches may be hard to spot, even if you have the coordinates!

Geocaching is an outdoor treasure-hunting activity that uses Global Positioning System (GPS)-enabled devices. It can also be a valuable public service.

Geocachers often look for benchmarks—a type of [survey mark](http://celebrating200years.noaa.gov/survey_marks/welcome.html#look)—that make up the [National Spatial Reference System](/facts/nsrs.html) (NSRS), the foundation for all mapping and surveying activities in the United States. NOAA’s [National Geodetic Survey](http://www.ngs.noaa.gov/) (NGS) defines and maintains the NSRS. For more than 200 years, NGS and its predecessor agencies have collaborated with surveyors in both the public and private sectors to place benchmarks across the nation. More than 1.5 million of them were placed from the 1920s to the 1980s!

A benchmark is a brass, bronze, or aluminum disk set in bedrock or concrete. This collection of markers forms a network that surveyors use to accurately position other geographic points of interest. This ensures that everything “matches up” when people produce maps, mark off property boundaries, and plan, design, and build structures, roads, and bridges.

Since many NSRS benchmarks are nearly a century old, NGS wants to know when geocachers find a benchmark. Many have been disturbed and reset through the years, and as many as half of them may have been destroyed by construction projects. A geocacher who finds a benchmark, measures its coordinates with a handheld GPS device, and [reports the find to the National Geodetic Survey](https://geodesy.noaa.gov//surveys/mark-recovery/) is performing a valuable public service.

Did you know? - 

- You can help keep the [National Spatial Reference System](https://oceanservice.noaa.gov/facts/nsrs.html) up to date! If you find a survey marker during your travels, let us know about the markers' condition using [our online form](http://www.ngs.noaa.gov/cgi-bin/recvy_entry_www.prl).
# What is a historical map or chart?

## NOAA considers a historical map or chart any map or chart that is not used today because it is **out of date**.

![Map of New York Bay and Harbor from 1845. ](nybay-historical.jpg "Map of New York Bay and Harbor from 1845. ")

Map of New York Bay and Harbor from 1845.

The Office of Coast Survey maintains a historical map and chart collection of over 35,000 scanned, high-resolution images. The collection includes some of the nation’s earliest nautical charts, bathymetric maps, city plans, and Civil War battlefield maps.

Nautical charts are one of the most fundamental tools available to mariners, depicting the nature and form of the coast, the general configuration of the sea bottom, water depths, locations of dangers to navigation, locations and characteristics of human-made aids to navigation, and other features useful to the mariner.

While the historical map and chart collection dates back to the 1700s, the Office of Coast Survey, which formed in 1807 as the first federal scientific agency, produced its first nautical charts in the mid-1830s.

Additionally, many of the historical maps in the collection depict events reflecting the geographic landscape at that time. One example is a Chattanooga battlefield map from 1863, which is considered one of the best Civil War maps at that time.

Digital copies of images within the collection are available for free download.