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Earth's Interior and Surface

Earth, the largest and densest rocky planet, was formed about 4.5 billion years ago. The Earth's interior is divided into four layers, which is typical of rocky planets. Each layer has different characteristics and is made of different elements and minerals.

There are many different types of features on Earth’s surface due to the complexity of our planet. The surface is unique from the other planets because it is the only one which has liquid water in such large quantities. Water forms some features of Earth's surface such as rivers, oceans, beaches and lakes. Other surface features, such as mountains, earthquakes and volcanoes, are formed when large pieces of the Earth’s outer layer move slowly by plate tectonics.

This is the Barringer Meteor Crater in Arizona. The diameter is 1.2
  kilomters, and it is 49,000 years old. Compared with other planets, <a
  href="/earth/Interior_Structure/crater.html&dev=1">impact
  craters</a> are rare <a
  href="/earth/Interior_Structure/surface_features.html&dev=1">surface
  features</a> on Earth. There are two main reasons for the low number of
  craters. One is that our <a
  href="/earth/Atmosphere/overview.html&dev=1">atmosphere</a>
  burns up most <a
  href="/our_solar_system/meteors/meteors.html&dev=1">meteoroids</a>
  before they reach the surface. The other reason is that Earth's surface is <a
  href="/earth/interior/plate_tectonics.html&dev=1">continually
  active</a> and erases the marks of craters over time.<p><small><em>D. Roddy and LPI</em></small></p>The most majestic of the volcanoes are composite volcanoes, also
  known as strato-volcanoes. Unlike the <a
  href="/earth/interior/shield_volcanos.html&dev=1">shield
  volcanoes</a> which are flat and broad, composite volcanoes are tall,
  symmetrically shaped, with steep sides, sometimes rising 10,000 feet high.
  They are built of alternating layers of <a
  href="/earth/interior/lava.html&dev=1">lava</a>
  flows, volcanic <a
  href="/earth/interior/ash.html&dev=1">ash</a>,
  cinders, blocks, and bombs.  This is a photo of Mt. Cotopaxi in Ecuador.<p><small><em>The U.S. Geological Survey</em></small></p>Shortly after 5 am on the 18<sup>th</sup> of April in 1906, most people in
  San Francisco, CA were awoken by a sudden jolt.  The Earth shook violently in
  a strong <a
  href="/earth/geology/quake_1.html&dev=1">earthquake</a>.
  It lasted for only about a minute, but caused a lot of damage which destroyed
  much of the city. This photograph was taken just after an earthquake and
  fires had ravaged the city.<p><small><em>                                                    National Archives Still Picture Records Section, Special Media Archives</em></small></p>Sinkholes are <a href="/teacher_resources/main/frameworks/esl_bi8.html&dev=1">natural hazards</a> in many places around the world. They are formed when water dissolves underlying <a href="/earth/Water/carbonates.html&dev=1">limestone</a>, leading to collapse of the surface.  Hydrologic conditions such as a lack of rainfall, lowered water levels, or excessive rainfall can all contribute to sinkhole development. On 2/28/2013, a sinkhole suddenly developed under the house outside of Tampa, Florida, leading to the tragic death of its occupant, Jeff Bush.<p><small><em>Image courtesy of Southwest Florida Water Management District</em></small></p>An <a href="http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc000905e.php">8.6 magnitude earthquake</a> struck on 11 April 2012 off of Banda Aceh, Sumatra, Indonesia, followed by a strong aftershock.  Earthquake motion was primarily horizontal.  A tsunami warning was issued for the Indian Ocean, but was cancelled at 12:36 UTC.  A tsunami was observed at 1 meter or less. Find out more about <a href="/earth/geology/quake_1.html&dev=1">earthquake</a> and <a href="/earth/tsunami1.html&dev=1">tsunami</a> processes. Check out the resources <a href="/teacher_resources/2011_AGU-NESTA_GIFT_Workshop.html&dev=1">here</a>.<p><small><em>NOAA</em></small></p>Hydrothermal vents in the deep ocean are located at tectonic <a
  href="/earth/interior/seafloor_spreading.html&dev=1">spreading
  ridges</a>. While most of the water in the deep ocean is close to freezing,
  the water at hydrothermal vents is very hot and laden with chemicals.  In
  this <a
  href="/earth/extreme_environments.html&dev=1">extreme
  environment</a>, certain species of <a
  href="/earth/Life/archaea.html&dev=1">Archaea</a>
  and <a
  href="/earth/Life/classification_eubacteria.html&dev=1">Eubacteria</a>
  thrive, enabling a unique <a
  href="/earth/Water/life_deep.html&dev=1">food
  chain</a> including fish, shrimp, giant tubeworms, mussels, crabs, and clams.<p><small><em> Courtesy of NASA</em></small></p>

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