| A | B |
|---|
| basalt | a dark, dense igneous rock with a fine texture, found in oceanic crust |
| cinder cone | a steep, cone-shaped hill or mountain made of volcanic ash, cinders and bombs piled up around a volcano's opening |
| composite volcano | a tall, cone-shaped mountain in which layers of lava alternate with layers of ash and other volcanic materials; also known as a stratovolcano |
| crater | a bowl-shaped area that forms around a volcano's central opening |
| crust | the layer of rock that forms Earth's outer surface |
| dormant | said of a volcano that does NOT show signs of erupting in the near future |
| earthquake | the shaking that results from the movement of rock beneath Earth's surface |
| epicenter | the point on Earth's surface directly above an earthquake's focus |
| extinct | said of a volcano that is unlikely to erupt again |
| fault | a break in Earth's crust where slabs of rock slip past each other |
| geology | the study of the structure and composition of planet Earth |
| hot spot | an area where magma from deep within the mantle melts through the crust above it |
| igneous rock | a type of rock that forms from the cooling of molten rock at or below Earth's surface |
| inner core | a dense sphere of solid iron and nickel in the center of Earth |
| lava | liquid magma that reaches the surface; also the rock formed when liquid lava hardens |
| mantle | the layer of hot, solid material between Earth's crust and core |
| Mercalli scale | a scale that rates earthquakes according to their intensity and how much damage they cause |
| metamorphic rock | a type of rock that forms from an existing rock that is changed by heat, pressure or chemical reactions |
| outer core | a layer of molten iron and nickel that surrounds the inner core of Earth |
| P wave | Primary wave; a type of seismic wave that compresses and expands the ground |
| plate | a section of the lithosphere that slowly moves over the asthenosphere, carrying pieces of the continental and oceanic crust |
| pyroclastic flow | the expulsion of ash, cinders, bombs and gases during an explosive volcanic eruption |
| Richter scale | a scale that rates seismic waves as measured by a particular type of mechanical seismograph |
| S wave | Secondary wave;a type of seismic wave that moves the ground up and down and side to side |
| sediment | small, solid particles of material from rocks and organisms which are moved by water or wind |
| sedimentary rock | a type of rock that forms from particles from other rocks or the remains of plants and animals that are pressed and cemented together |
| shield volcano | a wide, gently sloping mountain made of layers of lava and formed by quiet eruptions |
| subduction | the process by which oceanic crust sinks beneath a deep-ocean trench and back into the mantle at a convergent plate boundary |
| trench | a deep canyon in the ocean floor |
| volcano | a weak spot in the crust where magma has come to the surface |
