6th grade Tectonic Plates Lesson

Continental drift &

Plate Tectonics

♦ Crust

♦ Mantle

♦ Core

Earth’s Internal Structure

Mantle

• These convection currents are responsible

for the movement of tectonic plates.

• They are created by heat from radioactive

decay inside Earth.

Convection

Currents

•Alfred Wegener proposed the
hypothesis that continents were once
joined together in a giant
supercontinent he called Pangaea

• He proposed that Pangaea had split
apart and the continents had moved
gradually to their present positions -
a process that became known as
continental drift.

CONTINENTAL DRIFT

CONTINENTAL DRIFT

The theory explains the how and why behind mountains,
volcanoes, and earthquakes, as well as how, long ago, similar
animals could have lived at the same time in the same place.

Wegener’s Evidence for

Continental Drift

Fossils of plants and animals of the same

species have been found on different continents

around the world.

•Pangaea about 200 million years ago, before it began
breaking up.
•Wegener named the southern portion of Pangaea
Gondwana, and the northern portion Laurasia.

•The continents about 70 million years ago.
•Notice that the breakup of Pangea formed the Atlantic Ocean.
•India’s eventual collision with Eurasia would form the
Himalayan Mountains.

•This is the position of the continents current day.
•The continents are still slowly moving, at about the speed
that your fingernails grow.
•Satellite measurements have confirmed that every year the
Atlantic Ocean gets a few inches wider!

•If you look at a world map, you may notice that some of the continents
look like they could fit together. (like pieces of a puzzle)

Continents fit together
like a puzzle….e.g. the
Atlantic coastlines of
Africa and South
America.

Wegener’s Evidence for

Continental Drift

Pangea puzzle

Tectonic Plates

Plate Tectonics

• The Earth’s crust is divided into 6 major plates

which move in various directions.
Eurasian, African, Indo-Australian,
Pacific, North American, & South American.

• These plates movement causes them to collide,

pull apart, or scrape against each other.

• Each type of interaction causes a geological event

such as Earthquakes, Mountains, and Volcanoes.

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Continental Drift

Boundaries

• The most dramatic changes and land features

on Earth often occur along plate boundaries.

• Some plate boundaries run along the ocean

floor, others are on edges of continents or
within continents.

• Each type of plate boundary is associated with

a different type of land feature.

• Divergent

• Convergent

• Transform

Three types of plate boundary

• Divergent boundaries - are where two plates

move away from each other

• This separation allows hot rock below to melt. Magma

rises and erupts out of volcanoes on Earth’s surface,
where it becomes lava. Lava cools to form new rock.

Divergent Boundaries

• Iceland has a divergent plate

boundary running through the
middle.

Results of Divergent Boundaries

• Ocean basin
• Scars on earth
• Valleys
• Anything that separates
the Earth.

Divergent Rift in Iceland

• Convergent boundaries - are where two

plates collide with each other

Himalayas

Results of Convergent Boundaries

• Mountains

Formation of the Himalayas

• Transform boundaries – are where two

plates move past each other horizontally

the San Andreas fault in California
is a major transform boundary.

• The plate edges do not slide smoothly, instead they may

get stuck or locked with each other until they suddenly
slip. When a slip occurs, huge amounts of energy is
released causing earthquakes.

Chain of active
volcanoes are
mostly focused
at plate
boundaries

Pacific “Ring of Fire”

Ring of Fire

…what’s the connection?

Volcanoes and Plate

Tectonics…