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ISL #___
How the Earth Was Made: Mount St. Helens
Integrated Science 4
Name
5/16
Per.
 Introduction
Hot spots are zones where unusually high heat flow has been recorded at the Earth’s surface.
More than 100 such locations are known, and most occur along active plate boundaries. Iceland, the
location of a divergent boundary, also is a hot spot. But others, such as the Hawaiian Islands, are found
well within tectonic plate boundaries. These hot spots are isolated and not associated with spreading
centers or subduction zones.
The cause of hot spots is believed to be plumes of motlen rock welling up from the mantle. How
the plumes are formed is not well known but these sites often experience spectactular volcanic activity.
The volcanoes of Hawaii are a famous example that began to form more than 70 million years ago. Each
island was created by one or more volcanoes which started forming on the sea floor and eventually
emerging as an island after immeasurable eruptions.
Northwest of the inhabited Hawaiian Islands is a row of volanci peaks, which are located below
sea level. They are called the Emperor Seamounts. Though the Hawaiian Islands and the Emperor
Seamounts meat at an angle, they appear to be part of a single 4000 mile long continuous chain of
volcanoes called the Hawaiian-Emperor Chain.
It is inteststint to note that of the entire chain, only the Big Island (Hawaii) and the undersea
volcano Loihi are still volcanically active. These volcanoes are located farthest to the southeast and have
the highest heat flow. Perhaps the unusual arrangement of these volcanic islands and seamounts can be
explained by the movement of the Pacific Ocean floor over a stationary hot spot. If so, this evidence
would provide support for the theory of plate tectonics and its underlying mechanism of sea-floor
spreading.
This activity is designed for studetns to analyze the arrangement of the Hawaiian Island volcanoes
and determine a relationship between their age and location. As you work, consider these questions:
What is the relationship between the Hawaiian volcanoes and plate tectonics? How fast is the Pacific Plate moving?
How fast has it moved in the past?
 Hypothesis
Create a hypothesis as you gather and analyze your data.
 Procedures
1. Use the map provided and a metric ruler to measure the distance from the island of Hawaii to each
island or seamount listed below. Make all measurement along the island chain (not across the water).
Additionally, measure from the middle of the dot to the middle of the next dot. Record your
measurements in the Data Table.
2. Use the map scale to convert your measured distance (cm) to actual distance (km). Record these
conversions in the Data Table.
3. Use the completed Data Table to answer the Discussion and Conclusion questions.
 Data Table
Island/Seamount
Hawaii
West Maui
West Molokai
Waianae (Oahu)
Kauai
Nihoa
Measured Distance (cm)
0
Actual Distance (km)
0
Age/Last Eruption (mya)
Recent
1.3
1.8
3.6
5.6
7.5
Necker
10.0
Midway
16.2
Kanmu
38.0
Koko
46.0
Suiko
41.0
 Data Analysis
1. Use the distance and age data from the Data Table and the equation below to determine the
spreading rate (distance/time) of the Pacific Plate between when Kanmu was formed and the
present day. Show your work. ]Your original answer should come out in km/million yr. Convert
that to cm/yr and box your final answer.]
(older island distance – younger island distance)
older island age – younger island age
2.
Follow thes same procedure (above) to determine the spreading rate between Koko and Kanmu.
Remember to use the difference between their distsance and age from the formula.
 Discussion
1. Describe the location for the current source of magma. What is the relationship of this location to the
other islands/seamounts in the volcanic chain?
2. Discuss the relationship between island location and age data and the
theory of plate tectonics.