investigating earth's interior

• volcanoes extrude molten rocks that formed at great depths.
• once on earth's surface, they provide evidence of the processes that occur on earth's interior.
• when molten rocks erupt onto the surface as lava, the release of pressure expels trapped gases in a process known as outgassing.
• meteorites are the remains of meteoroids on earth.
• meteorites provide samples of materials from extraterrestrial objects that can be directly studied.
• scientists believe that meteorites are fragments of small planets or the once molten core of large asteroids.
• some meteorites are composed of materials that are in the core, mantle, and the crust of terrestrial planets.
• meteorites underwent differentiation
• processed meteorites were once part of a larger object whose original material, solar nebula, changed into another form.
• other processed meteorites have much lower densities and are much more similar to a planet's crust or mantle.
• geologists study lava flow to learn about earth's interior
• geoscientists collect rock samples containing iron and measure the magnetism recorded in rocks.
• the crust is separated from the underlying mantle by a boundary called the Mohorovicic discontinuity
• Mohorovicic discontinuity is named after Croatian seismologist and meteorologist Andrija Mohorovicic, who established its existence.
• in 1914, a major boundary was discovered by German-American seismologist Beno Gutenberg
• the discovery of the Gutenberg discontinuity supported Mohorovicic's theory that there is layering within Earth
• the region where a direct seismic wave is absent is called the P wave shadow zone
• P wave shadow zones covers an area of about 37 degrees
• observations of seismic waves also enabled scientists to learn that S waves could not propagate through the core.
• the mantle is the thickest layer
• the crust is the thinnest layer