Lab 3.2 – Plate Tectonic Settings
Fundamental concept: Recognize the relationship between bathymetry and earthquakes and connect real-world relationships to background knowledge.
Estimated time to complete: 20 minutes
Data skills preparation: Lab 1.2 geography, Lab 2.3 – Bubble Charts
Materials needed: Computer
In this activity you will overlay earthquake location data and relate that data to the features you observed and labeled in the previous activity. Using the relationship between the bathymetry and earthquake data, determine the various plate boundaries and types. First, use this map of bathymetry and earthquakes in the northeastern region of the Pacific Ocean to make observations and answer the questions below.
How to use the widget: If you hover over the map and scroll with your mouse the map will zoom in or out. You may also use the zoom features on the left to zoom in/out of the area in a more contolled method. In addition, you can move the map around by clicking and dragging it. [Note: if you accidentally scroll on the map and lose the data area – scroll out to see the continents and then proceed to drag the map to view the west coast of the U.S. You are looking for the NW United States and look for a large grey rectangle and then zoom in to it.] Under the map you can choose the timeline to look at by dragging the highlighted area. You may also automatically select a set timeframe and slide it right or left to view data from different years, those highlighted on the bottom timeline slidebar will appear on the map above it when the “show earthquake epicenters” is turned on by checking the box next to it.
To answer the following questions, toggle on the earthquake epicenters. Zoom in and out of the map and examine the relationship between earthquake magnitude and depth relative to the seafloor features within the study area, indicated by the rectangle on the map.
- Across what time periods are you able to observe oceanic or geologic variables in the plot?
- What is the first year that there are data?
- What is the last year that there are data?
Now toggle on the earthquake epicenters. Adjust the slider to add or remove epicenters.
- What is the range of earthquake magnitude?
(compare the data with the bathymetric and seafloor features from Lab 3.1)
- Referring back to Lab 3.1, what areas have the most earthquakes?
- Based on the concentration of earthquakes and the location and shape of seafloor features, what type of tectonic settings or boundaries are present and where are they located?
- What might the number of earthquakes at the mid-ocean ridge and transform zone indicate about plate movement? Is there a lot of motion occurring or not much?
- Which relationships between seafloor features and earthquakes are obvious?
- Why are so many earthquakes occurring in these areas?
- Referring back to Lab 3.1, what type of plate boundary apparently has the smallest magnitude earthquakes according to this data? Does this make sense? Why or why not?