LITHOSPHERIC PLATES. EQ: How do the lithospheric plates movement affect Earth’s surface? Lesson 19.

LITHOSPHERIC PLATES

EQ: How do the lithospheric plates

movement affect Earth’s surface?

Lesson 19

Lithospheric Plates• What features of Earth are

produced by the movement (colliding and sliding) of lithospheric plates?

• What was Alfred Wegener’s hypothesis?

• What is a scientific hypothesis?

• What does the collision of two continental plates produce? (example)

Cornell Notes – Lithospheric Plates

• What does the collision of a continental plate and a oceanic plate produce? (example)

• What does the collision of two oceanic plates produce? (example)

• What is produced when two plates slide by each other? (example)

How has the Earth changed in the last 250 million years?

Lithospheric Plates

• Earth's surface is like a jigsaw puzzle in motion• The pieces in the puzzle are made of large chunks of Earth’s lithosphere

• Lithosphere is the solid outer layer of Earth• It includes the crust and the top of the mantle• The moving chunks of the lithosphere are called lithospheric plates

• Continents and the ocean floor rest on these plates• Where these plates collide or separate, events take place that shape Earth’s surface

What is the Lithosphere?

• Lithosphere- The solid, outer layer of the Earth that consists of the crust and the rigid upper part of the mantle.

• Divided into pieces

called tectonic plates.

The Major Plates of Our Lithosphere

What was Alfred Wegener’s hypothesis?

Continental Drift

Continents in Motion• German scientist, Alfred Wegener (VAY guh nuhr ), hypothesized

that all land masses on Earth had once made up a single, giant continent.

• A hypothesis is a proposed explanation for one or more observations.

• As millions of years passed, pieces of this giant continent separated and moved to their present positions

• This process is called continental drift• Continents move about 2 cm a year

Continents in Motion• After years of observations

Wegener came up with a hypothesis he called continental drift.

• He thought all the continents were once joined in a single, huge continent.

• CONTINENTAL DRIFT- The hypothesis that states that the continents once formed a single landmass, broke up, and drifted to their present locations.

Evidence Number 1: Fossils

• Fossils can show evidence of continental drift• For example, Mesosaurus was a reptile that lived more than 250 million years ago

• It lived in freshwater lakes and rivers• Scientists found its fossils in both South America and Africa

• These continents are now separated by the salty Atlantic Ocean

• How did their remains end up on both continents?

Fossil Evidence

More Fossil Evidence

•Mesosaurus & Lystrosaurus- found in places now separated by oceans

•Glossopteris- fernlike plant found in rocks in Africa, S. America, Australia, India & Antarctica

More Fossil Evidence

Evidence Number 2: Landforms

• Continents puzzle-like fit

• Mountain ranges of Africa and South America line up

Coal Deposits

European coal fields match up with similar coal fields in North America

Evidence Number 3: Climate

• Island of Spitsbergen•Lies in Arctic Ocean; harsh, polar climate

•Fossils of tropical plants found here

•Glaciers•Evidence of past continental glaciers found in rocks of South Africa

What are the three types of Boundaries?

Events Caused by Moving Plates

• Scientists divide Earth’s lithospheric plates into two groups-• Less dense continental plates• More dense oceanic plates

The movement of these plates produce different events on Earth’s surface

Continental Plate vs. Continental Plate

• When two continental plates collide, neither slides under the other

• The plates buckle upward where they meet• This buckling produces mountain ranges• Example: the Himalayas in Asia

Continental collides with Continental

Oceanic Plate vs. Oceanic Plate• When two oceanic plates meet, one slides under the other• This action is called subduction. The area in which this

takes place is called a subduction zone.• A deep trench in the ocean floor forms and volcanic islands

may pop through the ocean’s surface.• The Aleutian islands between Alaska and Russia were

formed this way

Oceanic Plate vs. Continental Plate• When an oceanic plate runs into a continental plate, the more

dense plate slides under the less dense plate (subduction)

• This causes volcanic mountains like Mount St. Helens in the state of Washington to form.

Earthquakes!• Some plates get stuck as they push into each other or slide

past each other.• When they become unstuck, a sudden jolt happens.• Energy is released and energy sends waves through the

ground. (seismic waves)• This causes the ground to shake…It’s an earthquake!

Earthquakes Part 2• Earthquakes occur more frequently along plate boundaries

than anywhere else.• This accounts for the “Ring of Fire” that curves around the

Pacific Ocean.• The “Ring of Fire” is a belt where volcanoes and earthquakes

are very common.• The belt follows the borders of plate boundaries.

Ring of Fire

Quick Check

1. What features of Earth are produced by the movement of lithosphere plates?

A. solid masses of iron and nickel

B. liquid masses of iron and nickel

C. red-hot magma

D. mountains ranges, volcanoes, and volcanic islands

Quick Check

2. What was Alfred Wegener’s hypothesis?

A. The continents have always been where they are now.

B. Today’s continents were once part of a single land mass that split apart.

C. The continents are made of rock.

D. The continents will one day join to form a single continent.

Quick Check

3. Earthquakes are MOST LIKELY to occur at the borders of

A. continents.

B. lithospheric plates.

C. countries.

D. oceans

Quick Check

4. A scientific hypothesis is

A. a fact.

B. an explanation that has been supported by repeated observations and experiments.

C. a proposed explanation for one or more observations.

D. a guess that is not based on observations.

Quick Check

5. The collision of two continental plates can produce

A. volcanic islands.

B. a mountain range.

C. a single mountain

D. a trench.

Quick Check6. When two plates converge, one plate is usually forced to

slide under the other. Oceanic plates are more dense than continental plates. If an oceanic plate collides with a continental plate, what will be the likely result?

A. The continental plate will slide under the oceanic plate, generating an oceanic trench.

B. The oceanic plate will slide under the continental plate, generating an oceanic trench.

C. The continental plate will slide under the oceanic plate, generating an earthquake.

D. The oceanic plate will slide under the continental plate, generating an earthquake.

Quick Check

7. If two plates meet at a convergent boundary and do not form a subduction zone, they may

A. fold.

B. fault.

C. weather.

D. erupt.

Quick Check

8. The process of seafloor spreading occurs at what kind of plate boundary?

A. divergent

B. convergent

C. transform

D. at both convergent and transform boundaries

Quick Check

9. Where does magma come from?

A. the inner core

B. the outer core

C. the mantle

D. the lithosphere

Quick Check

10. The ancient supercontinent, Pangea, once contained

A. all of the Earth’s tectonic plates.

B. all of Earth’s crust.

C. all of Earth’s continental crust.

D. all of Earth’s oceanic crust