Formation Of Crustal Features

Tension

• Tension: Forces within a plate can cause the plate to break into sections, some of which sink, while other sections rise.

An example is the Teton Mountains in Wyoming. The state of Nevada is broken into a series of such mountains

Mountain Building

When one continental plate converges with another continental plate, the two plates are squeezed together with compressional forces. Over time, the rock layers can fold and fracture, creating "folded" mountain chains parallel to the boundary.

When an ocean plate subducts under a continental plate, compressional forces at the edge of the continent plate will also create some folding mountain.

When one ocean plate subducts under another ocean plate, magma from the subducting ocean plate pushes back to the surface, forming chain or arc of volcanic islands.

Earth's Layers

Plate Tectonic Theory

Structurally, the Earth has five layers.These layers are affected by both pressure and heat, which both increase with depth.

• Inner Core: is mostly solid iron and nickel. It has temperatures over 5000* C.
• Outer Core: As the Inner Core, but the lower pressures allow the metals to melt. The movement of the metal creates the Earth's magnetic field.
• Mesosphere: Is the lower, mostly solid part of the mantle. Temperatures and pressures are lower than the outer core.
• Asthenosphere: Is the upper, semi-liquid part of the mantle. Temperatures and pressures are lower than the outer core
• Lithosphere: Is the outermost layer of solid rock. It has the lowest temperature and pressure.

According to this theory, the lithosphere (which includes the crust) is broken into nine major and many smaller tectonic plates, which float on the denser semi-liquid asthenosphere.Convection current of thick molten rock in the asthenosphere move the plates slowly over millions of years, opening up gaps that fill with lava, colliding plates together to build mountains, and subducting ocean crust to form volcanic mountains.

Tectonic Plate Boundary Types

There are three main types of tectonic plate boundaries: convergent, divergent and transform.

• Divergent Boundary: Occurs when two plates move away. This can either happen o a continent, creating a new rift valley, or under the ocean at a mid-ocean ridge.
• Transform Boundary: Occurs when the two plates are sliding past one another in opposite directions. The San Andreas Fault in California is a transform bounndary.
• Convergent Boundary: Occurs when two plates converge.

Earth's Layers

Earth's layers are classified in two different ways; chemically and physically.

Chemically~

• Core: made largely of the metals iron and nickle
• Mantle: made of dense rock rich in iron
• Crust: A thin surface layer made of lese dense rocks rich in aluminum and magnesium

Formation of Crustal Features

Antonio Rivera and Ashley Sandoval