Earth Processes

Geology =

the scientific study

of our planet Earth

• How would you describe the Earth’s Surface?

• How did the surface get this way?

Plate Tectonics• The lithosphere is broken into 20 sections

called PLATES• Each PLATE is a huge slab of rock that

includes the crust• Fit together like a jigsaw puzzle• Page 218• Plates float on layer of partly melted rock• Can move 2cm – 15cm/yr

Why do they move??• CONVECTION CURRENTS cause plates

to move

• Convection currents cause hot matter to rise while cool matter sinks

• MAGMA moves up and spreads out sideways in a circular pattern

• Magma carries the plates with it

To Review…• The sections of the lithosphere are called

A. CrustsB. PlatesC. Puzzle pieces

• Convection currents causeA. Cool magma to rise and hot magma to sinkB. Hot magma to rise and cool magma to sinkC. The movement of the Earth’s platesD. Both B & CE. Both A & C

Plate Tectonics• Changes will occur in the Earth’s

crust where 2 plates meet• A FAULT is a crack in the Earth’s

crust along which rock moves• Each plate boundary is a huge fault

(226)

Faults

1. Fracture boundary = two plates sliding past each other• San Andreas Fault

Faults

2. Spreading boundary – plate moving away from each other and new crust added to the surface

• Great Rift Valley

Faults

3. Colliding boundary = plates move toward each other = mountains

• Himalayas

To Review• At which type of fault would the plates

move into each other and cause mountains to form?

• At which type of fault would plates slide past one another?

• At which type of fault would plates move away from each other?

A. Fracture boundary

B. Spreading boundary

C. Colliding boundary

Writing for Science

• Write a letter to a 2nd grader telling them what you learned about Plate Tectonics today

• Must include:– What the earth’s crust is made of– What causes the plates to move– How much the plates move in a year– What a fault is

Earthquakes

• Plates will get caught on each other• Pressure builds until rock breaks

and lurches forward• An earthquake is a sudden shaking

or vibrating of the Earth’s crust• Most occur along plate boundaries

(228)• Built up energy is released

Earthquakes

• The focus is where the first rock moves

• Waves move out that make the ground shake = ground rolling, shaking or lifting

• The Epicenter is directly above on the Earth’s surface

Earthquakes• Types of Seismic Waves –

– S-waves (secondary)• Make rock move up and down and side to

side, deep underground

– P-waves (primary)• Deep below the ground they stretch and

squeeze the rock particles

– L-waves (long)• Travel along the surface• Causes the most damage

Earthquakes• Seismograph is the instrument records the

seismic waves of energy that radiate from the focus of an earthquake

• Richter Scale is a series of numbers used to describe the total amount of energy released, or magnitude of an earthquake (1930)

– Each increment is 10x stronger

• Tsunamis are caused by earthquakes under the sea that generate a powerful wave that travels to the surface

To Review• Which type of wave moves along the surface of

the earth during an earthquake?

A. S-waves

B. L-waves

C. P-waves• The first rock moves at the ________.

A. Epicenter

B. Focus

To Review• What is the name of the instrument that

records the seismic wave that occur during an earthquake?

A. Richter Scale

B. Seismograph

C.Tiltmeter

Volcanoes• An opening in the Earth’s surface

through which magma rises

• Most occur at the plate boundaries and hot spots

• Many on the ocean floor

• Try to predict to save lives

• Tiltmeter – detects change in slope of volcano = magma might be moving

Volcanoes

MAGMA

VENT

LAVA

CRATER ASH & CINDERS

Volcanoes• Eruptions depend on

– Water vapor and gases in magma• If escaping easily = quiet eruptions• Under pressure = explosive eruption

– Lava• Vicious lava (thick and sticky) has gas

that escapes with force and throws ash high in the air

• Non-viscous lava is thin and runny and lava will flow from the vent

Volcanoes• At a subduction/colliding boundary

1. Sinking crust melts into magma as it enters the mantle

2. Hot magma is less dense than solid rock

3. Magma rises through openings in crust

4. Gases in magma cause pressure to build

5. When pressure is great enough – magma breaks through surface as LAVA

Volcano Types

Composite = formed from alternating eruptions of cinders /ash & lava•Above subduction zones•Mt. Saint Helen’s

Volcanoes• At a Hot Spot

1. Areas in mantle hotter than others

2. Magma has melted through the crust

3. This will form several volcanoes that will turn in to islands (Hawaii)

Volcano TypesShield = quiet eruptions that spread

out in flat layers

•Forms a broad volcano with gently sloping sides

•“New real estate”

•Hawaiian Islands

Volcano Types

Cinder cone = steep sided volcano

•Form from explosive eruption of lava, ash and cinders

•Steep with small crater

•Form rapidly

•Paricutin

To Review

• Quiet volcanic eruptions result fromA. Water vapor and gases under tremendous

pressure

B. Water vapor and gases escaping easily

To Review

• The type of volcanoes that are created at subduction zones are

A. Cinder

B. Composite

C. Shield

To Review

• The type of volcanoes that are created at areas where the mantle is hotter than the crust are

A. Cinder

B. Composite

C. Shield

To Review

• When magma reaches the surface of a volcano it is called

A. A crater

B. A vent

C. Cinder

D. Lava

Soil Formation• Why is soil important?• Soil = mixture of weathered rock and decayed

plant and animal (organic) matter formed over a long time

• Also includes mineral fragments, water and air• Weathering = process of rock breaking into

smaller and smaller fragments• Humus = dark colored organic matter made of

pieces of decaying plants and animals• Worms mix the humus with rock fragments

Soil Profile• Topsoil –

– Dark– Contains humus– Worms

• Subsoil– – Little or no humus– Some plant roots– Minerals washed down

from topsoil• Bedrock –

– Weathered rock– No humus– Beginning the process of

becoming soil

Rock Cycle