Earth's Structures

shearing

Breaking off

basalt

Igneous rock that makes up the oceanic plates

compression

Pressing together under great pressure

oceanic crust

Solid outer zone of the Earth that includes the oceanic plates

volume

The amount of space that a substance or object occupies, or that is enclosed within a container

supercontinent Pangea

About 300 million years ago, Earth didn't have seven continents, but instead one massive supercontinent called Pangaea, which was surrounded by a single ocean called Panthalassa.

mass

Amount of matter in an object (we measure this with a scale).

subduction zone

Area in which oceanic lithosphere is carried downward (subducted) under an island arc or continent at a convergent plate boundary. A trench usually forms at the boundary between the two converging plates.

fault

Area where continental plates either converge, subduct, shear, or

continental drift

Continental plates shifting their position on the Earth's crust over millions of years of riding around on the moving mantle

granite

Igneous rock that makes up most of the continental plates. Granites can be predominantly white, pink, or gray in color, depending on their mineralogy.

homogeneous

Made of the same material throughout

density

Mass per unit volume

dense

Matter that has high mass per unit of volume

plasticity

Matter that moves like thick wet concrete or thick fudge before it has cooled. You see "plasticity" in pictures of lava oozing out of the Earth or a volcano.

igneous rock

Rock formed when molten rock material (magma) wells up from the Earth's interior, cools and solidifies into rock masses.

metamorphic rock

Rock produced when a pre-existing rock of any type is subjected to high temperatures and/or pressure, chemically active fluids, or a combination of these agents. The original rock is "changed"

sedimentary rock

Rock that forms when the accumulated products of erosion, and in some cases from the compacted shells, skeletons, and other remains of dead organisms are cemented together by pressure or chemical reactions. Many fossils are found in "sedimentary rock"

continental crust

Solid outer zone of the Earth that includes the continental plates

outer core

The core of the Earth is like a ball of very hot metals. (4000 degrees F. to 9000 degrees F.) The outer core is so hot that the metals in it are all in the liquid state. The outer core is located about 1800 miles beneath the crust and is about 1400 miles thick. The outer core is composed of the melted metals nickel and iron.

lithosphere

The crust and the upper layer of the mantle together make up a zone of rigid, brittle rock called the Lithosphere.

crust

The crust is composed of two basic rock types granite and basalt. The continental crust is composed mostly of granite. The oceanic crust consists of a volcanic lava rock called basalt. The Earth's Crust is like the skin of an apple. It is very thin in comparison to the other three layers. The crust is only about 3-5 miles (8 kilometers) thick under the oceans(oceanic crust) and about 25 miles (32 kilometers) thick under the continents (continental crust). The temperatures of the crust vary from air temperature on top to about 1600 degrees Fahrenheit (870 degrees Celcius) in the deepest parts of the crust. The crust of the Earth is broken into many pieces called plates. The plates "float" on the soft, plastic mantle which is located below the crust. Notice how thin the crust of the Earth is in comparison to the other layers. The seven continents and ocean plates basically float across the mantle which is composed of much hotter and denser material.

aesthenosphere

The layer below the rigid lithosphere is a zone of asphalt-like consistancy called the asthenosphere. The asthenosphere is the part of the mantle that flows and moves the plates of the Earth.

inner core

The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick. The temperatures may reach 9000 dgrees F. and the pressures are 45,000,000 pounds per square inch. This is 3,000,000 times the air pressure on you at sea level!!!

convection current

The mantle is made of much denser, thicker material, because of this the plates "float" on it like oil floats on water. Many geologists believe that the mantle "flows" because of convection currents. Convection currents are caused by the very hot material at the deepest part of the mantle rising, then cooling, sinking again and then heating, rising and repeating the cycle over and over. The next time you heat anything like soup or pudding in a pan you can watch the convection currents move in the liquid. When the convection currents flow in the mantle they also move the crust. The crust gets a free ride with these currents. A conveyor belt in a factory moves boxess like the convection currents in the mantle moves the plates of the Earth.

mantle

The mantle is the layer located directly under the crust. It is the largest layer of the Earth, 1800 miles thick. The mantle is composed of very hot, dense rock. This layer of rock even flows like asphalt under a heavy weight. This flow is due to great temperature differences from the bottom to the top of the mantle. The movement of the mantle is the reason that the plates of the Earth move! The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom!

plate tectonics

Theory of geophysical processes that explains the movements of lithospheric plates and the processes that occur at their boundaries.

tectonic plates

Various sized areas of the Earth's lithosphere that move slowly around with the mantle's flowing aesthenosphere. Most earthquakes and volcanoes occur around the boundaries of these plates.

convergent plate boundary

Where two lithospheric tectonic plates are pushed together (converged).