Download Earthquake Depth Data - Hillview Middle School

Name:
Subduction Lab
Period:
The vast majority of earthquakes occur at plate boundaries. The deepest earthquakes
occur at subduction boundaries where lithosphere is plunging down into the mantle.
The behavior of the subducting plate is determined by the age of the rocks comprising
the plate. Older crust is cooler, and therefore denser, than younger crust. Older, cooler, denser
crust subducts faster and at a steeper angle than younger, warmer, less dense crust.
In this lab activity, you will plot and compare actual earthquake depth data from two
areas where subduction is currently occurring. One of the areas includes the Tonga Islands in
the southwest Pacific Ocean. The other area is along the coastline of Chile.
Procedure:
On the graph on page 2, plot the data for Tonga and
Chile trenches from the table. DON’T CONNECT THE
DOTS, wait for teacher’s ok to do so.
 Assume the lines outline the converging plates
 Label the approximate location of the Tonga and
Chile trenches on the graph
 Using your Plate Boundary Map, indicate the
name of the two converging plates
 Using your Plate Boundary Map, indicate the
relative movement of each plate using arrows
 Using your Plate Boundary Map, indicate the
type of crust that makes up each plate.
Earthquake Depth Data
Tonga Trench
Longitude Depth
(°W)
(km)
174
0
174.5
25
174
50
175
50
175.5
100
174
150
175
150
176
150
174.5
175
176
200
175.5
250
176
250
175.5
300
176.5
300
177
400
177.5
375
176.5
400
177.5
450
178
450
178
500
178.5
500
178
550
178
600
178.5
600
178.5
650
179
650
Chile Trench
Longitude Depth
(°W)
(km)
69
25
68.5
50
65.5
50
68
50
67
100
70
25
69
75
66
100
65.5
100
69
125
67
150
65
150
66.5
150
65.5
200
64.5
175
68.5
125
65
225
62.5
275
68
100
66.5
200
66
225
64.5
300
62
300
61
350
62
425
65.5
250
Reflection Questions:
1. Which tectonic plate is being subducted at the Tonga Trench?
2. Which tectonic plate is being subducted at the Chile Trench?
3. Notice the direction that the Nazca and Pacific plates are moving. What process is occurring at
the boundary of those two plates?
4. Look at your plate boundary map. Where do you usually find divergent boundaries (plates
moving away from each other)?
5. The boundary between the Nazca and Pacific plate is part of the East Pacific Rise. If new rock
(sea floor) is being formed at the East Pacific Rise, which trench (Tonga or Chile) should contain
the oldest rock? Why? (Complete sentences)
6. What type of geologic feature is found at a subduction zone?
7. Based on the data you plotted in the lab, the collision of which two types of plates (oceanicoceanic, oceanic-continental, continental-continental) creates the deepest earthquakes? Use
specific data from the lab to prove your statement. (complete sentences)