Plate Tectonics Notes Part 1

Plate Tectonic Theory

Evidence for

Plate Tectonics

Plate Tectonics Notes Part 1

Unveiling the Secrets of Continental Drift and Plate Tectonics

The Puzzle of Continental Drift

• Continental drift: the theory that continents have moved over time
• Alfred Wegener: proposed the theory in 1912
• Evidence: matching coastlines, fossil records, rock formations
• Plate tectonics: explains how continents move on Earth's surface

•Alfred Wegener in the early
1900’s proposed the hypothesis
that continents were once joined
together in a single large land
mass he called Pangea (meaning
“all land” in Greek).

• He proposed that Pangea 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

According to the hypothesis of
continental drift, continents
have moved slowly to their
current locations.

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.

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

Impacts of Continental Drift

• Formation of Mountains: Continental drift leads to the collision of tectonic plates, resulting in the formation of mountains like the Himalayas.

• Volcanic Activity: Plate tectonics cause volcanic eruptions, releasing gases and creating new landforms.

• Climate Change: Shifting continents affect ocean currents, leading to changes in climate patterns.

• Biological Evolution: Separation and merging of landmasses influence the evolution and distribution of species.

Multiple Choice

Which scientist proposed the theory of continental drift?

• Alfred Wegener

• Isaac Newton

• Albert Einstein

• Charles Darwin

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

The Best fit includes the
continental shelves (the
continental edges under
water.)

Wegener’s Evidence for

Continental Drift

Picture from
http://www.sci.csuhayward.edu/~lstrayer/geol2101/2101_Ch19_03.pdf

Wegener’s Evidence for

Continental Drift

Fossils of plants and animals of the

same species found on different

continents.

Picture from
http://volcano.und.edu
/vwdocs/vwlessons/pla
te_tectonics/part3.ht
ml

Wegener’s Evidence for

Continental Drift

• Rock sequences (meaning

he looked at the order of
rock layers) in South
America, Africa, India,
Antarctica, and Australia
show remarkable
similarities.

• Wegener showed that the

same three layers occur
at each of these places.

•

Picture from
http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/p
art4.html

Wegener’s Evidence for

Continental Drift

• The same three layers are

in the same order in areas
now separated by oceans.

• Wegener proposed that

the rock layers were made
when all the continents
were part of Pangaea.

• He proposed that they

formed in a smaller small
joined land mass that was
later broken and drifted
apart.

Picture from
http://volcano.und.edu/vwdocs/vwlessons/plate_tectonics/p
art4.html

Multiple Choice

Which evidence supports the idea of continental drift?

• Matching fossils found on different continents

• Similar rock formations and mountain ranges

• Ancient climate indicators

• The jigsaw-like fit of continents

Multiple Choice

What is one of the effects of continental drift and plate tectonics?

• Formation of mountains

• Formation of oceans

• Formation of deserts

• Formation of forests

Seafloor Spreading

• Everyone agreed that Wegener’s evidence was

compelling. But wouldn’t we feel the
movement?

• Also, wouldn’t there be evidence to show that

the continents were still moving today?

• Wegenerwas a meteorologist and his theory

was not well accepted. (He died on an
expedition in Greenland collecting ice samples)

​Wegener

What was the problem?​

​

Wegener couldn't explain WHY or HOW the continents moved!

​

The scientific community needed more than what Wegener had.

​

Later, Harry Hess made a discovery that helped!​

Seafloor Spreading

• Hess proposed that hot,

less dense material
below Earth’s crust rises
toward the surface at
the mid-ocean ridges.

• Then, it flows sideways,

carrying the seafloor
away from the ridge in
both directions.

Picture from http://library.thinkquest.org/17457/platetectonics/4.php

Seafloor Spreading

• As the seafloor spreads apart at a

mid-ocean ridge, new seafloor is created.

• The older seafloor moves away from the

ridge in opposite directions.

• This helped explain how the crust could

move—something that the continental
drift hypothesis could not do.

Picture from
http://www.pbs.org/wgbh/aso/tryit/tectonics/divergent.html

​What is causing seafloor spreading? To understand, we must look at the layers of the Earth.

​Crust, where we live. Broken in pieces called "tectonic plates"

​

Two types of crust: Oceanic and Continental.​

​Oceanic

Crust​

​Continental

Crust

​Inside of your notes:

​What is the difference between the continental crust and oceanic crust?

​

Continental crust is LESS DENSE, the oceanic crust is MORE DENSER.

​The hottest layer of the Earth is the core. It heats the mantle above it. When the magma heats up, it rises.

​

What effect might this have on the crust?​

​Oceanic

Crust​

​Continental

Crust

​Inside of your notes:

​Inner

Core​

​Outer

Core​

​Mantle

​Convection in the Mantle

What are

convection currents?

• one of 3 ways that

energy is transferred
from one object to
another.

• Heat transferred by

movement of a
heated fluid

​Hot magma rises, cold magma falls.

​

What do we call this process of hot rising and cold falling/sinking?​

Multiple Choice

The hypothesis that land masses spread apart from each other and have done so in the past is known as

• Seafloor Spreading

• Continental Drift Theory

• Uplift of the crust

• Continental Spreading

Multiple Choice

Where does sea-floor spreading take place?

• Convergent Boundaries

• Transform Boundaries

• Land Boundaries

• Mid-Oceanic Ridges

Multiple Choice

What is the thinnest layer of the Earth?

• Crust

• Mantle

• Outer Core

• Inner Core

Multiple Choice

What is the thickest layer of the Earth?

• Crust

• Mantle

• Outer Core

• Inner Core

Plate Tectonic Theory

• Both Hess’s discovery of

seafloor spreading and
Wegner’s continental drift
theory combined into what
scientists now call the Plate
Tectonic Theory.

• Theory of plate tectonics:

• The Earth’s crust and part of the

upper mantle are broken into
sections, called plates which
move on a plastic-like layer of
the mantle

Plate Tectonic Theory

• Plate Tectonics explains

– Earthquakes
– Mountain formation
– Volcanoes
– Why continents move

What are Plate Tectonics?

•

Definition - geological theory that
explains formation, movement, and
subduction of Earth’s plates

•

So exactly what does this mean?

•

3 things

1.

Lithosphere is in constant motion (1-10 cm/year)

2.

Motion is slow

3.

Caused by convection currents

What is a plate?

• The cracks in the lithosphere section it off

into 14 different plates

• Move very slowly (1-10 cm a year)
• These plates carry

– Continents
– Oceans
– Some carry both continents and oceans

14 Lithospheric Plates

• Ocean plates (Pacific, Nazca)

• Ocean/Continent Plates (Eurasian,

Indo-Australian, Antarctic, North American,
South American, Caribbean, African,
Filipino, Scotia, Arabian, Cocos, Juan de
Fuca)

Divergent
Convergent
Transform

EARTHQUAKES AND PLATE TECTONICS

VOLCANOES AND PLATE TECTONICS

Multiple Choice

Scientists hypothesize that a super continent existed 200 million years ago.  This continent is called

• America
• Super Earth
• Pangea
• Eurasia

Multiple Choice

Alfred Wegener thought which 2 continents looked like puzzle pieces that could fit together?

• Antarctica and Asia

• South America and Africa

• South America and Australia

• Africa and Pangaea

Multiple Choice

What geologic feature will form at a hot spot?

• volcano

• folded mountain

• deep sea trench

• rift valley

Multiple Choice

What is the source of energy that drives plate movement?

• the subducton of the sea floor

• the different densities of the oceanic and crustal plates

• convection currents in the asthenosphere

• the friction force between the plates that move past each other

Audio Response

Provide an audio summary about what you learned today. In your summary you should include information about continental drift, plate tectonics, earthquakes, and volcanoes.

Open Audio Recorder