Hawaiian Hot Spot
63 points total
Review the text on hot spot volcanism and recall that hotspots produce a string
of dormant volcanoes behind an active volcano. Because we know the age of the
volcanoes and their distance from the hot spot we can use the dormant volcanoes
produced by a hot spot to determine the speed and direction that a tectonic
plate is moving. This exercise will guide you through that process.
There are a couple
of different ways to do this. One would be to recognize that if a dormant
volcano is 5 million years old and is sitting 450 km from a hot spot then it
has moved 450 km in 5 million years. If we divide 450 by 5 we get 90
km/Ma. That unit is kilometers per
million years (Ma is an abbreviation for millions of years). This is not a
particularly useful unit. A million years is a very long time so it’s difficult
to really understand how fast a speed given in km/Ma really is. For most of
what we do we measure speeds in miles per hour. You know how long and hour is
and you know how far a mile is so it’s a useful unit. For Plate tectonic
velocities it’s best to measure the speed in centimeters per year (cm/yr).
Doing this gives a number usually between 5 and 15 or so which is a very useful
and manageable unit. Since there are 100,000 centimeters in a kilometer
converting from km/Ma to cm/yr is relatively easy: divide my 10. So 90 km/Ma is
Use the map below
to figure out how fast the Pacific plate has been moving since Oahu formed over
the hot spot. The questions on the next page will guide you through the
___________ km/Ma (5 points)
technique is useful it’s limited in that it doesn’t take advantage of all the
data we have. We have age and distance data for the entire Emperor Seamount
Chain as well as the Hawaiian islands. The following exercise will guide you
through the process of using all the available data to learn about the speed
and direction that the Pacific plate has been moving.
First the data.
|#||Name||Age (Ma)|| Distance|
from the hotspot (km)
|50|| Pearl &|
Volcano 91 Suiko 2
age (x) ____________Ma, Distance (y) ____________ km (4 points)
Volcano 1 Kilauea
age (x) ____________ Ma, Distance (y) ____________ km (4 points)
Difference in the x
values ____________ Ma. Difference in the y values ____________ km (4 points)
(Subtract the two numbers above the blanks)
Now divide the
difference in y by the difference in x:
____________km / ____________Ma=____________
km/Ma (4 points)
convert km/Ma to
cm/yr (like you did in question # 4)
Speed of the
Pacific tectonic plate ____________ cm/yr (2 points)
Now that we’ve done
speed, let’s do direction. Look at the map below.
Note that there is
a bend in the seamount chain (labeled bend). The Daikakuji seamount is located
right at the bend.
between the formation of Meiji and
Daikakuji? ________________ (3 points)
______________ (3 points)
So there you are,
you just used real geoscience data to do what real geoscientists do, you
calculated the speed and direction of a tectonic plate.
Turn the word file
with your answers into the drop box. Photograph or scan the graph name it with
your name and turn it in to the drop box as well.
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