Lab 10 plate tectonics
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Geography 101 Plate tectonics
Geography 101
Lab 10
Plate Tectonics
Introduction: In 1912 German geophysicist and meteorologist
Alfred Wegener publicly presented in a lecture, his idea that
Earth’s large landmasses migrate. His book called, The
Origins of Continents and Oceans, appeared in 1915.
Wegener today is regarded as the father of this concept called
continental drift. Wegener postulated that all landmasses
were united in one supercontinent approximately 225 million
years ago, during the Triassic period. This one landmass he
called Pangaea, meaning all Earth.
His proposal launched a half-century debate leading up to the
adoption of plate tectonics as an all-encompassing theory of
continental drift, sea floor spreading and subduction. Aided
by an avalanche of discoveries, the theory today is nearly
universally accepted as an accurate model of the way Earth’s
surface evolves, and virtually all Earth scientists accept the
fact that lithospherical masses move about.
The Breakup of Pangaea: The figure below gives you the
opportunity to work with an updated version of Wegener’s
Pangaea, 225 to 200 million years ago (Triassic-Jurassic
periods). Areas of North America, North Africa, the Middle
East, and Eurasia were near the equator and therefore were
covered by plentiful vegetation. The landmasses focused near
the South Pole and attached to the sides of Antarctica were
covered with ice. We also see that Africa shared a common
connection with both North and South America. The
Appalachians and the Atlas Mountains of North America
and Africa reflect this common ancestry; they are in fact,
portions of the same mountain range.
The Atlantic Ocean
did not exist. The only oceans were Panthalassa, which
would become the Pacific and the Tethys Sea which
eventually formed the Mediterranean Sea, with trapped
portions becoming the present-day Caspian Sea.
The figure above shows Pangaea as it was 200 to 225 million years ago. Alfred Wegener used paleoclimatic evidence to support his
idea of plate tectonics. For example, there were tropical regions that have since been glaciated, while mid-latitude areas were once
tropical swamps. For this section, you will identify locations that had very different climates in the past. For this assignment we will
assume that we are looking at Permian conditions, when global temperatures were similar to current temperatures. You will have to
estimate climate and biome locations using latitude (it is in 10-degree increments on the map above) and continentality to compare
them to present climatic locations. For example, Northern India was located at roughly 35 S latitude and on the east coast of a large
land mass.
A location with a similar climate today would be China which has a humid subtropical climate. This is how the Earth
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Geography 101 Plate tectonics
continents are located today (latitude and longitude lines are in 20-degree increments. Please number the latitude and longitude lines
on the maps above and below.
This is how the Earth continents are located today
World Climates and their guidelines
Questions: Refer to the world maps above to
answer the following questions. This will likely
be easiest if you print in color and have the
maps next to each other rather than having to
scroll up and down.
1.
For b – e below, write the letter on
the map of Pangaea in the
appropriate location. The first
location is done for you as an
example.
Use the maps of the world
climates and the current configuration
of the globe to assist you. The first
one is completed and there is a dot on
the map of Pangaea on the continent
of Africa. That dot is in the tropical
rainforest today but on the map of
Pangea it was located at about 30 S
(desert ).
a.
A location that was a desert (under subtropical high), but is now a rainforest (tropical)
b.
A location that would have been glaciated (arctic or Antarctic), but is now tropical
c.
A location that was tropical but is now in the mid-latitudes
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Geography 101 Plate tectonics
d.
A location that was a rainforest, but is now a desert
e.
A location that would have been glaciated but is now arid
f.
A location that has changed location the least
2.
To visualize the mechanisms that drive Earth’s lithospheric plates, refer to the figure below.
a.
At the time of Pangaea, South America and Africa were attached forming a continuous landmass. Explain the
process(es) that likely transpired over the past 225 million years to position the two continents where they are today.
b.
With respect to the movement of crustal plates in the vicinity of the Andes Mountains: What is the oceanic plate
diving beneath South America? How is this related to formation of the Andes? (The diagram below and the tectonic
plate map under #3 may be helpful)
3.
The figure below shows the tectonic features in modern
times.
A spreading center extends down the center of
the Atlantic and into the southern Indian Ocean.
Subduction trenches are active along the west coasts of
Central and South America and throughout the western
Pacific Ocean basin. The northern reaches of the India
plate (pictured below as the northern part of the Indo-
Australian plate) have under thrust the southern mass
of Asia through subduction, forming the Himalayas in
the upheaval created by the collision.
Of all the major plates, India traveled the furthest.
From approximately 150 million years ago until the
present according to Robert Dietz and John Holden,
more than half the ocean floor was renewed. The inset
blocks (below the map) demonstrate the types of specific
plate boundaries.
a.
Using the figure below, locate the following and determine what type of plate boundary they are (convergent,
divergent, or transform).
1.
On the ocean floor south of Alaska – Convergent Plate Boundary
2.
Indian Ocean between the Antarctic and Indo-Australian plates- Divergent Plate Boundary
3.
Beneath the Red Sea – Divergent Plate Boundary
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Geography 101 Plate tectonics
4.
Along the west coast of Central America – Divergent Plate Boundary
5.
Through Iceland – Divergent Plate Boundary
6.
Along the north east coast of the Persian Gulf- Convergent Plate Boundary
b.
Which three plates converge on Japan?
Eurasian, North American, and Philippine Plates
c.
What plate do you live on? North American, convergent plate boundary
4.
A dramatic aspect of plate tectonics is the estimated 50
to 100 hot spots across the Earth’s surface. These are
individual sites of plumes of upwelling material from
the continental crust and appear to be deeply anchored
in the mantle, tending to remain fixed relative to
migrating plates.
An example of an isolated hot spot is the one that has
formed the Hawaiian Emperor Islands chain.
The
Pacific Plate has moved across this hot, upward
erupting plume for almost 80 million years, with the
resulting string of volcanic islands moving
northwestward away from the hot spot. Thus, the age
of each island or seamount in the chain increases
northwestward from the Big Island of Hawaii. The
ages are in parentheses next to the name on the map.
The unit is million years
a.
Which is the youngest Hawaiian Island?
The youngest island is Hawai’I (Big Island)
b.
Which is the Oldest?
The oldest island is Ni’ihau (west of Kaua’i)
c.
The newest seamount, Lo’ihi, is 975 meters beneath the ocean surface.
If it is growing upward at 2 meters per year,
how long before it emerges from the sea? 487.5 years
d.
Use the map scale to find the linear distance from the hotspot’s present location to the Meiji Seamount? (Here is a
tutorial for the paper method of measuring distance on a map
https://youtu.be/ZEWH58yMsAQ
)
.
_________________________________
e.
The age of Midway Island is 27.7 million years
f.
The distance from Midway to the active hotspot is 1482.5 km
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Geography 101 Plate tectonics
g.
Using these values what is the average speed of the Pacific Plate? 53.7 km / million year
h.
What conclusions can be drawn about the direction the Pacific Plate has been moving based on the trend of the
Emperor Seamounts and the Hawaiian Island Chain?
i.
About how many millions of years ago did the plate change direction? 38.7 million years ago
j.
What does this indicate about the life span of a mantle plume? That it remains for hundreds of millions of years
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