Download Hot Spot LAB 2017 - eat, sleep, breathe science

Name ________________________________________ Date __________________Lab # __________
Lab Group Members: ________________________________, ________________________________
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The Theory of Plate Tectonics
and Hot Spots
Hawaii Hotspot (Crustal Plate Movement)
Introduction:
In 1963, J. Tuzo Wilson, the Canadian geophysicist who discovered
transform faults, came up with an ingenious idea that became known
as the "hotspot" theory. Wilson noted that in certain locations around
the world, such as Hawaii, volcanism has been active for very long
periods of time. This could only happen, he reasoned, if relatively
small, long-lasting, and exceptionally hot regions -- called hotspots -existed below tectonic plates that would provide localized sources of
high heat energy (thermal plumes) to sustain volcanism.
Wilson suggested that continuing plate movement eventually carries
the volcanic island beyond the hotspot, cutting it off from the magma
source, and volcanism ceases. As one island volcano becomes extinct, another develops over the
hotspot, and the cycle is repeated. This process of volcano growth and death, over many millions of
years, has left a long trail of volcanic islands and seamounts across the Pacific Ocean floor.
According to Wilson's hotspot theory, the volcanoes of the Hawaiian chain should get progressively
older and become more eroded the farther they travel beyond the hotspot.
Origin of the Hawaiian Islands
The Hawaiian Islands are the tops of gigantic volcanic mountains formed by countless eruptions of fluid
lava over several million years; some tower more than 30,000 feet above the seafloor. These volcanic
peaks rising above the ocean surface represent only the tiny, visible part of an immense submarine ridge,
the Hawaiian Ridge—Emperor Seamount Chain, composed of more than 80 large volcanoes.
This range stretches across the Pacific Ocean floor from the Hawaiian Islands to the Aleutian Trench,
Alaska. The length of the Hawaiian Ridge segment alone, between the Island of Hawai'i and Midway
Island to the northwest, is about 1,600 miles, roughly the distance from Washington, D.C., to Denver,
Colorado.
Procedure A:
1. Using Map 1 on this page and the absolute dates of lava in bold black numbers that represent
millions of years before the present. Calculate the age difference between the islands and
enter the data in the table on page 3.
2. Make distance measurements between the “dots” of each circle using the scale on the
diagram.
3. Convert the distance from kilometers to “land” or “real” centimeters (NOT what you
measure on the map!) by multiplying the distance in KM by 100,000 (which is the number
of cm in 1 km. HINT: This will be a big number!
4. Hawaii contains an active volcano, Mauna Loa, so the lava from it is zero years old (labeled
“.01”). The lava on Kauai Island is 5.1 million years old. Thus, according to the hot spot
hypothesis, Kauai Island was once an active volcano standing where Hawaii stands today.
Map 1
Distance
(km)
Islands
Land
Distance
(cm)
Difference in
Age
(years)
Rate of
Movement
(cm/year)
Hawaii - Maui
Maui - Molokai
Molokai – Oahu
Oahu - Kauai
5. Figure the rate in centimeters per year using the distances from Hawaii to each of the three dated
lavas on the map and the following rate equation.
Distance between islands (cm)
Rate of Movement =
Difference in Age (years)
Round your answers to the nearest tenth (0.1 cm/year)
6. Now calculate the rate of movement or the average speed of crustal movement and round to the
nearest 0.1.
Average rate =
7.
cm/year
In which direction was the crustal plate apparently moving when the Hawaiian Islands were
formed? ________________________________________________
Explain how you can tell.
8. According to your data, did the crustal plate always move at the same speed? Explain your
answer. ______________________________________________________________________
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Part B: Graphing tectonic plate movement over time:
A hot spot is a stationary hot area underneath a tectonic plate. Hot magma from Earth;s mantle
travels through cracks in the crust at a hot spot and forms a volcano. If the Pacific plate did not move,
there would only be one volcano over the hot spot. But as the plates moves, the old volcano moves
along with the crust exposing new areas of crust to the hot spot and allowing a new volcano to form.
The result is a chain of islands with the youngest island, over the hot spot. This formation gives
scientists the unique ability to calculate the rate of movement and determine the direction of
movement of tectonic Plates based on the age of each island and the distance between them.
DATA:
The following are islands that are part of the Hawaiian chain and their age
Island
Km away from hot spot
Age (million years
old) 0
Kilauea
0
Kohala
1
0.4
Lanai
20
1.3
0
Kauai
52
5.1
16
Necker
1058
10
9
.3
Brooks Bank
1256
13
.0
Northampton
1841
26
Bank
.6
Midway
2432
27
.7
Abbott
3280
38
.7
Yuryaki
3520
43
.4
Koko
3758
48
.1
Suiko Central
4860
64
.7
PROCEDURE:
A. Make a graph. On the horizontal X axis you will plot the distance from the hotspot.
B. On the vertical Y axis you will plot the age using the data above. The range for the horizontal axis
should start at zero and go up by 200’s to 5200.
C. Staple your graph to the back of the lab when completed. Make sure your graph has title, labels,
units.
Interpret your graph:
1) Look at the graph. The slope of the line tells you the rate (or speed) of the plate movement. Based
on your graph, has the rate of movement been constant through time? If not explain where/when it
was faster? Slower? Explain the reason for your answer by referring to specific ages on the graph.
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2) Estimate from your graph: if you find rock that is 55 million years old, how far would it be
from the hot spot?
Think about it:
Hot spots are places where magma is coming up through Earth's crust that are not necessarily
located at a plate boundary. As the plates move over the hot spot volcanic islands can form.
The block diagram below shows the bedrock age as measured by radioactive dating and the
present location of part of the Hawaiian Island chain. These volcanic islands may have formed as
the Pacific Plate moved over a mantle hot spot.
Use the diagram to the right to answer the following
questions.
1. Which island is the youngest?
2. Which island is the oldest?
3. Which compass direction was the Pacific crust
moving toward?
4. A new island is already forming off the coast of
Hawaii named Loihi. By looking at the diagram to
the right, what compass direction (from Hawaii) is
Loihi forming?
The cross section below shows the direction of movement of an oceanic plate over a mantle hot spot,
resulting in the formation of a chain of volcanoes labeled A, B, C, and D. The geologic age of volcano C
is shown.
5.
What are the most likely geologic
ages of volcanoes B and D?
a. B is 5 million years old and
D is 12 million years old.
b. B is 2 million years old and
D is 6 million years old.
c. B is 9 million years old and
D is 9 million years old.
d. B is 10 million years old and
D is 4 million years old.
Base your answer to the question on the world map below and on your knowledge of Earth science.
The map shows major earthquakes and volcanic activity occurring from 1996 through 2000. Letter A
represents a volcano on a crustal plate boundary.
6.
Explain why most major earthquakes are found in specific zones instead of being randomly
scattered across Earth’s surface.
7.
Identify the source of the magma for the volcanic activity in Hawaii.
8.
Identify the type of plate movement responsible for the presence of the volcano at location A.