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 3 main layers:

1.Crust2.Mantle3.Core

Composition

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

The Crust

2 Types of Crust1. Continental crust: - land bodies, usually

30 km thick! (Mostly granite)

2. 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

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

The Core

Physical Properties of Earths Layers

• Based upon structure, there are 5 physical layers:

1.) Lithosphere2.) Asthenosphere3.) Mesosphere4.) Outer core 5.) 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.

•Lower part of the mantle

3.) Mesosphere

•Outer liquid layer of the core

4.) The Outer Core

•Solid inner layer of the core

5. Inner Core

Tectonic Plates• Pieces of the lithosphere that move

around on the asthenosphere.• Made of continental crust, oceanic

crust or both

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

Depths of the Earth

The device that measures seismic waves is a seismograph.

Seismic Waves

Section 1 Recap QuestionsWhat 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

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

Alfred Wegener1911

Wegener’s Theory explains some observations:

1.  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?

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

Plate Tectonics

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.) Convergent2.) Divergent3.) 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

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

1.Compression2.Tension

Compression

Motion that Occurs

–Rock is squeezed & will fold

What type of boundary?

–Convergent

Tension

Motion that Occurs

–Rock is stretched and can break

What type of boundary?

–Divergent

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

Folding

3 Types of folding:

1. Anticline2. Syncline3. Monocline

Anticline

Description: rock folds downward (like a hill)

Picture:

Syncline

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

Picture:

MonoclineDescription: layers of rock

are stacked but remain horizontal.

Picture:

Fault

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

•The blocks of crust on either side of the fault

Fault Blocks

•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

Hanging Wall

Footwall

3 Types of Faults 1.Normal2.Reverse3.Strike-slip

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:

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

1. Folded2. Fault-block3. 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.

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

Volcanic Mountains