Science Inside The Earth

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Composition of the Earth

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The Earth is divided into three layers - the crust, mantle and core - based on the compounds ( or substances) that make up each layer

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Crust

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The thin, solid, outermost layer of the Earth

The thinnest layer of the Earth (5-100km)

It has two forms - continental and oceanic

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Contental crust

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Is located above water and is 30 km to 100 km thick

It is composed of oxygen, silicon and aluminum

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Oceanic crust

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Is located under the ocean and is about 5 km thick.

It is composed of oxygen, silicon and aluminum but has twice as much iron, calcium and magnesium.

It it denser than continental crust

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Mantle

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Is the layer of crust between the crust and the core.

It is much thicker than the crust and contains most of the Earth's mass.

It is too far to reach so scientists make conclusions about its composition and physical properties

It has more magnesium and less aluninum and silicon than the crust

It is more dense than the crust

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Core

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The center of the Earth

The layer below the mantle

Made mostly of iron, contains small amounts of nickel and almost no oxygen, silicon, alunimum or magnesium

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physical structure of the Earth

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The Earth is divided into five physical layers - lithosphere, asthenosphere, mesoshpere, outer core and inner core

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lithosphere

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The outermost rigid layer of Earth

Made of two parts - the crust and the rigid upper part of the mantle

divided into pieces called tectonic plates

15 to 300 km thick

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asthenosphere

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The plastic layer of the mantle on which pieces of the lithosphere move

Made of solid rock that flows very slowly

250 km thick

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mesosphere

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Located beneath the asthenosphere

It is the strongest lower part of the mantle

extends from the bottom of the asthenosphere to the Earth's core, 2,550 km thick

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Outer Core

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Liquid layer of the Earth's core that lies beneath the mantle and and surrounds the inner core

2,200 km thick

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Inner core

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The solid denser center of the planet that extends from the bottom of the ourter core to the center of the Earth

6,380 km beneath the surface

1,230 km thick

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Tectonic plates

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pieces of the lithosphere that move around the top of the asthenosphere

The block of the lithosphere that consists of the crust and the rigid outermost part of the mantle

They have names like the Pacific plate and the North American plate and the African Plate

They are like pieces of a jigsaw puzzle on the lithosphere

Are made up of continental crust and oceanic crust

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mapping the Earth's interior

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Scientists use seismographs to map the Earth's interior

Seismic waves travel through solids and liquids at different speeds. Measuring the speed of the waves allows scientists to determine what the Earth is made up of.

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Continental drift

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the hypothesis that states that the continents once formed a single land mass, broke up and drifted to their present locations

A hypothesis created by Alfred Wegener

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seal floor spreading

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The process in which new oceanic lithosphere forms as magma rises to the surface and solidifies

As magma rises from mid ocean ridges it cools and solidifies. That pushes the tectonic plates apart.

The older crust is farthest away from the mid ocean ridge and the newest crust is forming at the mid ocean ridge where the magma is coming up.

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Magnetic reversal

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is evidence of sea floor spreading

iron deposits occur naturally in he rock on the sea floor. Scientists monitor the magnetic poles of the rock. The reversals in magnetic poles is evidence of sea floor spreading.

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Theory of plate tectonics

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The theory that the Earth's lithosphere is divided into tectonic plates that move around the top of the asthenosphere

the plates meet at plate boundaries

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Tectonic plate boudndaries

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Where tectonic plates touch

the 3 types of plate boundaries are convergent, divergent and transform

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convergent boundaries

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When two tectonic plates collide

There are three types: Continintal-continental
Continental-oceanic
Oceanic-oceanic

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Continental-Continental boundary

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when two tectonic plates with continental crust collide

The collided crusts bulk and thicken, which pushes the continental crust upward

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Continental-oceanic boundary

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when a plate with an oceanic crust collides with a plate with a continental crust.

The denser oceanic crust sinks into the asthenosphere (or converges)

The special name for the converging boundary is subduction zone

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subduction zone

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When a continental crust collides with oceanic crust and the oceanic crust is pushed down into the asthenosphere. The rock melts and is recycled.

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Oceanic-oceanic

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when two tectonic plates with lithosphere collide, one lithosphere is subducted (or sinks) under the other plate

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Divergent boundary

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when two tectonic plates separate

New sea floor forms here

mid ocean ranges are the most common type

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transform boundaries

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when two tectonic plates slide past each other horizontally

San Andreas fault in California is an example. It is where the Pacific and North America plates are sliding past each other

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Plate movement causes

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rock in the asthenosphere gets heated. The cooler more dense material at the top sinks down and the hotter melter rock material flows up. This movement occurs in three ways:
ridge push, convection and slab pull

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Ridge push

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tectonic plate movement that occurs at a mid ocean ridge when the oceanic lithosphere is higher than where it sinks into the asthenosphere and the oceanic lithosphere lsides downhill under the force of gravity

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convection

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hot rock from deep within the earth rises but cooler rock at the surface sinks, the oceanic lithosphere moves sideways and away from the mid ocean ridge

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slab pull

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because oceanic lithosphere is denser than asthenosphere the edge of the tectonic plate that contains oceanic lithosphre sinks and pushes the rest of the tectonic plate with it

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GPS

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used to track plate movement by monitoring the changes in distance between plates and satellites

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Deformation

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The process in which the shape of rock changes because of stress.

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Compression

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the type of stress that occurs when rock is squeezed like when two tectonic plates collide.

occurs at a convergent boundary and may cause large mountain ranges to form

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Tension

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Stress that occurs when forces act to stretch rock.

Occurs at divergent plate boundaries like mid oceanic ridges where tectonic plates are pulling away from eachother

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Folding

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The bending of rock layers because of stress on Earth's crust

Types of rock folds are:
anticlines are "n" shaped or upward arching folds

synclines are "U" shaped or downward troughlike folds

monoclines or a horizontl line that dips down and flattens out again

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anticlines

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"n" shaped or upward arching folds

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synclines

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"U" shaped or downward troughlike folds

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monoclines

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a horizontal rock layer that dips down and flattens out again

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fault

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The place where rock breaks and slides when stress is applied

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Fault blocks

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Blocks of crust on each side of the fault

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Hanging wall

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When a fault line is slanted the fault block on one side will be wider at the top and narrow at the bottom - like you can hang from it

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Footwall

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when the fault line is slanted the fault block on one side will be narrow at the top and wider at the bottom - like you could put your foot on it and walk up

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Normal fault

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when this type of fault moves it causes the hanging wall to go down.

This type of fault usually occur where tectonic forces cause tension and pull the plates apart

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Reverse fault

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when this type of fault moves is causes the hanging wall to move up

This type of fault usually occurs when tectonic forces cause compression which pushes rocks together

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Slip-strike fault

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This type of fault forms when opposite forces cause the rock to break and move horizontally

These are transform boundaries where plates slide past each other horizontally

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Folded , fault block and volcanic

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The three types of ways mountains are formed by tectonic plates

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Folded mountains

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They are the highest mountain ranges in the world

They form at convergent boundaries where continents have collided

They form when rock layers are squeezed together from compression stress and are pushed upward

Himalayas and the Alps

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Fault block mountains

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When tectonic forces cause tension and stretch the earth's crust enough, a large number of normal faults result.

These mountains form when the tension causes large blocks of the earth to drop down.

Sedimentary rock layers are tilted up by several normal faults and it causes mountains with sharp jagged peaks

The Tetons

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Volcanic mountains

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Most of the world's major mountains of this type are located at convergent boundaries where oceanic crust sinks into the asthenosphere at subdiction zones

Melted rock in subduction zones forms magma, which rises to the earth's surface and erupts to form this type of mountain

These mountains can form undersea and can rise above the surface to become islands

Most have formed around the ring of fire in the Pacific ocean

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Uplift

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The rising of regions of earth's crust to higher elevations

The rocks that go through this process may or may not have deformation

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Subsidence

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The sinking of regions of eart's crust to lower elevations

The rocks that go through this process have little deformation

As the heated lithosphere at the mid oceanic ridge cools and becomes denser as it is pushed further away from the mid oceanic ridge and subsides

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Rebound

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Uplift that occurs when large regions of rock moves up without deforming


Crust slowly springs back to its previous elevation because a weight is removed from the crust

Earthquakes occur when this happens

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Rift zone

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a set of deep cracks that form between two tectonic plates that are pulling away from eachother.

As the plates pull apart stress between the plates cause a series of faults to form along this area. The blocks of crust in the center of this area subside