Inside the Earth

Part 1.

Earth is made up of how many main layers?

5

Inner core

Made of iron and nickel solid because of intense amounts of pressure. 746 miles thick from radius, 6,100 degrees Celsius (due to nuclear fission creating heat).

Outer core

Mix of nickel and iron (liquid). Has convection currents that create the magnetosphere. It is 5,500 degrees Celsius.

Which layers make up 14% of Earth’s volume?

Inner and outer core.

Mantle

Solid layer that is 1740 miles thick. There is a mix of silicates near the top with magnesium and iron the deeper you go.

Asthenosphere

The layer that is fluid but is not a liquid. It’s a solid layer with high malleability. Part of the upper mantle that drives plate tectonics by pulling the lithosphere with convection currents.

Convection

Transfer of heat through movements of heated liquids, where warm, less dense material rises and cooler, denser material sinks.

Mohorovicic discontinuity

Separates the asthenosphere and the lithosphere. Where earthquake waves change velocity.

What two layers make up 84% of Earth’s volume?

Upper and lower mantle.

Lithosphere

The rigid, but brittle layer that makes up tectonic plates (62 miles thick on average). Subsidence causes heavy continents to sink.

Oceanic crust

A solid, brittle layer (3-5 miles thick) mostly composed of basalt (contains silicates and some iron). Denser than continental crust. Part of the outermost layer (crust). Found beneath oceans.

Continental crust

Another solid, brittle layer (part of the outermost layer, the crust), 5-25 miles thick. Made of mostly granite. Forms the continents.

Which goes above; oceanic crust or continental crust?

Continental crust goes above oceanic.

Lithosphere

Thinnest, outermost layer of the Earth.

Lithosphere contains what other layers?

Crust and a small part of the upper mantle.

What layer is beneath the lithosphere?

Asthenosphere.

What is beneath the asthenosphere?

Mesosphere.

Which flows more slowly; mesosphere or asthenosphere?

Mesosphere.

Tectonic plates

Pieces on top of the asthenosphere. Some contain oceanic lithosphere, continental lithosphere, or both.

How do scientists know about Earth’s interior?

Studying earthquakes using seismometers (measures the seismic waves)

Seismic waves

Vibration waves from earthquakes.

Continental drift

A hypothesis developed by Alfred Wegener that all the continents were once one big landmass.

Sea-floor spreading and magnetism

Patterns on one side of a mid-ocean ridge was a mirror image of the pattern of the pattern on the other side of the ridge (caused by magnetic reversal).

Magnetic reversal

North and South magnetic poles have switched places many times throughout history.

What happens where tectonic plates touch?

The place where tectonic plates meet are called boundaries.

3 types of tectonic boundaries

1. divergent boundaries

2. convergent boundaries

3. transform boundaries

Divergent boundaries

Where plates move APART (usually found underneath oceans).

convergent boundaries

where plates move TOGETHER

Transform boundaries

where plates SLIDE PAST EACH OTHER

Why do tectonic plates move?

3 possible explanations

1. Convection

2. Slab pull

3. Ridge push

Slab pull

Cold, sinking lithosphere at the edges of a tectonic plates pulls the rest of the plate across Earth’s surface.

Ridge push

Gravity pulls newly formed lithosphere downward and away from the mid-ocean ridge. The rest of the plate moves because of this force.

Convection currents

Convection currents are produced when hot material in the mantle rises toward the surface and colder material sinks. The currents pull the plates over Earth’s surface.

Deformation

Change in shape, size, or volume of an object or material when various amounts of stress.

Fault

A break in the Earth’s crust where blocks move past each other

Three different types

Hanging wall

The block that lies ABOVE the inclined geologic plane

Footwall

The block that lies BELOW the inclined geologic plane.

Normal fault

The HANGING wall moves DOWN. Forms when rocks are put under stress.

Where are NORMAL faults most common?

Divergent boundaries

Reverse faults (also called thrust faults)

The HANGING wall moves UPWARD relative to the wall. Created by squeezing and/or compression forces that shorten the crust.

Strike-slip faults

Fault blocks slide PAST each other HORIZONTALLY

How do mountains form?

Edges of the plates grind against each other, creates stress on earth’s lithosphere.

What are 3 ways mountains can form?

1. Folded

2. Faulting

3. Volcanism

Folded mountains

When rock layers are squeezed together and pushed UPWARD (usually at CONVERGENT boundaries)

Fault-block mountains

Forms when tension makes the lithosphere break into many NORMAL FAULTS

Subsidence

Gradual sinking/settling of Earth’s surface

What causes subsidence and uplift in Earth’s surface?

Temperature changes

As hot rocks cool, they may ____

Sink

As cold rocks are heated, they may ____

Rise

Volcanism

where molten rock, gas, and ashes break through Earth’s surface (usually happens when tectonic plates crash together/move apart)

Why does ocean crust far from a mid-ocean ridge subside?

The crust rocks cool down

Old, cold crust far from a ridge has a lower elevation than what?

Young, hot crust at the ridge

If glaciers melt, what happens to the weight on the crust?

It decreases.

When glaciers form on the crust, they do what to it?

Subside the crust (push it down).

Rift zone

A set of deep cracks that form at a DIVERGENT BOUNDARY.

Rift valley

A dropped zone where 2 tectonic plates are pulling apart

What are the 5 main layers of the Earth?

Lithosphere, asthenosphere, mesosphere, outer core, and inner core