<span style="font-family: comic sans ms;color: violet;font-size: medium">• Earthquakes form when there is a vibration in the earth’s crust, causing a sudden release of energy. This energy is radiated out from the quake’s epicenter, in the form of seismic waves. </span> <span style="font-family: comic sans ms;color: violet;font-size: medium">• There are two types of seismic waves, the P-waves, or primary waves and the S-waves, also known as secondary waves. The P-Waves are the first waves to arrive during an earthquake. They compress and dilate (push together and pull apart) rocks in the ground, and they can travel through solids and liquids. The S-waves arrive after the P-waves. They move more slowly than the P-waves.As they pass through the ground they cause the rocks to move from side to side.</span> <span style="font-family: comic sans ms;color: violet;font-size: medium"><img src="http://library.thinkquest.org/03oct/01530/images/seismicwaves.gif" alt="" /></span>

Volcanoes form when hot material from below <a href="http://www.windows.ucar.edu/tour/link=/glossary/plumes.html">rises</a> and leaks into the crust. This hot material, called magma, comes either from a melt of subducted crustal material, and which is light and buoyant after melting, or it may come from deeper in the interior of a planet and is light and buoyant because it is *very* hot.

Magma, rising from lower reaches, gathers in a reservoir, in a weak portion of the overlying rock called the <a href="http://www.windows.ucar.edu/tour/link=/earth/interior/magma_chamber.html">magma chamber</a>.  Eventually, but not always, the magma <a href="http://www.windows.ucar.edu/tour/link=/earth/interior/eruptions.html">erupts</a> onto the surface. Strong earthquakes accompany rising magma, and the volcanic cone may swell in appearance, just before an eruption, as illustrated in this picture. White arrows in the picture show the volcano getting bigger as magma rises inside. Scientist often <a href="http://www.windows.ucar.edu/tour/link=/earth/interior/volcano_monitoring.html">monitor</a> the changing shape of a volcano, especially prior to an eruption.   The different reasons why a volcano forms are
<ul>
	<li>via <a href="http://www.windows.ucar.edu/tour/link=/earth/interior/plume_volcanism.html">plumes</a> or hot spots in the lithosphere</li>
	<li>as a result of <a href="http://www.windows.ucar.edu/tour/link=/earth/interior/subduction.html">subduction</a> of the nearby lithosphere</li>
</ul>
<span style="text-decoration: underline"><strong>Week of Nov 9</strong></span>

<strong>Alfred Wegener</strong>- The creater of the theory of plate tectonics

<strong>Theory of plate tectonics</strong>-that large plates bearing continents and oceans move about on the planet because of earthquakes, mountain building, and valcanoes

<strong>Divergent Boundaries-Plates pull away from each other</strong>

<strong>Convergent Boundaries- Plates move toward each other</strong>

<strong>subduction- creates volcanoes (two plates move in together and one melts underneath the other)</strong>

<strong>tranformation- two plates rub against eath horizontally causing earthquakes</strong>

<strong>plate collisions- two plates hit into each other and move upward. This forms mountains</strong>