Chapter 4: Section 1: Inside the Earth

The Earth is made of different layers which are described by their Composition and Physical properties

The Earth is divided into Composition The Earth is divided into 3 main layers: Crust Mantle Core

The Crust The crust is the outermost layer of the Earth with a thickness of 5 to 100 km

2 Types of Crust Continental crust: - land bodies, usually 30 km thick! (Mostly granite) Oceanic crust: - bottom of water bodies, 5-8 km thick. (Mostly basalt)

Two types of crust

The Mantle thickness of 2,900 km. It is so deep that… no one has ever seen what it looks like. Contains most of the Earth’s mass

The Core Is the center of the Earth and is made of Iron with smaller amounts of Sulfur, Aluminum and Magnesium, and silicon and oxygen

Physical Properties of Earths Layers

Based upon structure, there are 5 physical layers: ) Lithosphere ) Asthenosphere ) Mesosphere ) Outer core ) Inner core

1.) The Lithosphere Outermost layer made up of the crust and the rigid upper part of the mantle. Divided into pieces called tectonic plates.

2.) The Asthenosphere This is the soft layer of the mantle on which pieces of the lithosphere move.

3.) Mesosphere Lower part of the mantle

4.) The Outer Core Outer liquid layer of the core

Solid inner layer of the core 5. Inner Core Solid inner layer of the core

Tectonic Plates Pieces of the lithosphere that move around on the asthenosphere. Made of continental crust, oceanic crust or both

Depths of the Earth Scientists cannot visit the depths of the Earth like the mantle and the core but use seismic waves recorded during earthquake activity.

Seismic Waves The device that measures seismic waves is a seismograph.

Section 1 Recap Questions What are the 3 main layers of the Earth? Crust, Mantle, Core What are the 2 components of the crust? Continental and Oceanic What is the largest layer of Earth? The Mantle According to their characteristics, what are the 5 layers Earth can be broken into? Lithosphere, Asthenosphere, Mesosphere, Outer core, Inner core

Alfred Wegener 1911 Developed a Theory called the Theory of Plate Tectonics which states that the Earth’s lithosphere is divided into tectonic plates that move around on top of the asthenosphere. The continents once formed a single landmass, broke up, and drifted to their present locations

Wegener’s Theory explains some observations:  The continents seem to fit together

2. Fossils of the same plant and animal species are found on continents that are on different sides of the Atlantic Ocean.

3. Similar types of rock were found on several continents.

4. Evidence of the same ancient climatic conditions were found on several continents.

Wegener proposed that all of the separate continents that we see today were once connected in a giant landmass called Pangaea which broke up about 180 M years ago and formed 2 big pieces called Laurasia and Gondwanaland. Then, about 65 MYA, these broke up and formed the continents that we know today.

Sea Floor Spreading As the tectonic plates move away from each other, the sea floor spreads apart and magma fills in the gap.

Sea floor spreading is proven by the ages of the rocks As this new crust forms, the older crust gets pushed away from the mid-ocean ridge. The older crust is farther away from the mid-ocean ridge than the younger crust is.

Magnetic Reversal Throughout Earth’s history, the north and south magnetic poles have changed places many times.

How does Magnetic Reversal Prove Sea Floor Spreading?

Plate Tectonics Theory of Plate Tectonics states that the Earth’s lithosphere is divided into tectonic plates that move around on top of the asthenosphere. The continents once formed a single landmass, broke up, and drifted to their present locations

Boundary Boundary - is a place where tectonic plates touch. 3 types of boundaries (depending on how the plates are moving relative to one another): 1.) Convergent 2.) Divergent 3.) Transform

Convergent Boundary Type of Crust  O-O, C-C, or O-C Type of Movement - 2 plates move together often, 1 oceanic plate moves under another oceanic or continental plate in a process called subduction Arrows - 

Divergent Boundaries Type of Crust  O-O or C-C Type of Movement - 2 plates move apart Arrows -

Stress Stress is: the amount of force that is applied on a given material.

Deformation - when rock changes shape due to stress

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There are two main types of stress that can act on a rock. Compression Tension

Compression Rock is squeezed & will fold Convergent Motion that Occurs What type of boundary? Convergent

Tension Rock is stretched and can break Divergent Motion that Occurs What type of boundary? Divergent

Folding Folding occurs when rock layers bend due to stress in the Earth’s crust.

3 Types of folding: Anticline Syncline Monocline

Anticline Description: rock folds downward (like a hill) Picture:

Syncline Description: rock folds upwards (like a “u”) Picture:

Monocline Description: layers of rock are stacked but remain horizontal. Picture:

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Fault A crack in the Earth’s crust along which rocks move.

Fault Blocks The blocks of crust on either side of the fault

If a fault is cut diagonally, it usually has two specific sides. a)Hanging wall: the upper side of the cut, the upper portion sticks out. b)Footwall: the lower side of the cut, the bottom portion sticks out

Hanging wall & Footwall

3 Types of Faults Normal Reverse Strike-slip

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Normal Faults Description: Stress at a divergent boundary pulls Hanging wall down relative to the footwall Picture:

Reverse Fault Description: Compression pushes Hanging wall moves up relative to the footwall at a convergent boundary Picture:

Description: Rock breaks & moves horizontally (transform boundary) Strike-Slip Fault Description: Rock breaks & moves horizontally (transform boundary) Picture:

Mountains Mountains are formed when tectonic plates undergo compression or tension.

3 Types of Mountains Folded Fault-block volcanic

Folded mountains Description: Rock layers are squeezed together & pushed upwards

Fault-Block Mountains Description: when there is enough tension, a large number of normal faults can result. Mountains are tilted upwards by faulting & will have sharp, jagged peaks.

Volcanic Mountains Description-When molten rock erupts into the Earths surface, magma pushes the surface of the Earth upwards