08 A GeoMapApp and Google Earth Exploration of the Mariana Subduction Zone

4/2018 A GeoMapApp and Google Earth Exploration of the Mariana Subduction Zone The objectives of this activity are:  To become familiar with comparing maps in Google Earth to those from GeoMapApp.  To understand the Bathymetry in and around the Mariana Subduction zone.  To understand the geologic processes going on in and around the Mariana Subduction zone.  To learn to use the GeoMapApp Distance/Profile tool.  To learn the location of the Challenger Deep. The Mariana subduction system is the place on Earth where the oldest ocean crust is subducting. It shows some very interesting features, including unusual Serpentinite Seamounts , which we explored during the International Ocean Discover Program (IODP) Expedition 366 from December 2016 through January 2017. You will explore the following areas:  The Mariana subduction area explored by IODP Expedition 366, including the serpentine seamounts, South Chamorro, Yinazao, Asut Tesoru, and Fantangisna.  The Mariana arc, its ridges.  The Mariana Trough.  The Mariana Trench.  The Challenger Deep. Requirements:  A current version of Google Earth. Google Earth is available for download for PC, Mac, or Linux.  A current version of Java, which is freely available for download for a variety of platforms, such as Windows, Mac OS, and various versions of UNIX.  A current version of GeoMapApp. GeoMapApp is a Java-based geographic system (GIS) developed and maintained at the Lamont- Doherty Earth Observatory’s Marine Geoscience Data System. It is freely available for download.  The file IODP Expedition 366.kmz (from Canvas).  The Smithsonian Global Volcanism Network’s Google Earth placemark files of the global Holocene volcanoes. This is also used in the exercise Plate Tectonics as Expressed in Geological Landforms and Events: An Exploration Tip: Use Google or another search engine to look for Java and / or GeoMapApp and follow the instructions to download and install the correct version for your computer and operating system.

Introduction to Earth Science 08 GeoMapApp & Google Earth Exploration of Mariana Subduction Zone using Google Earth. If you completed that exercise, you should have this file already loaded in your “My Places” menu in Google Earth. Part 1: Google Earth Overview of the IODP Expedition 366 Exploration Area. A. The IODP Expedition 366.kmz file includes placemarks for the four serpentine seamounts that were visited (South Charmorro, Yiazao, Asut Tesoru, and Fantangisna seamounts and the ship track, which started in Guam and finished in Hong Kong. The other prominent feature in the Mariana subduction zone is the Mariana Trench, which is the deepest of all the deep-sea trenches around the world. Questions: 1. Where are these seamounts relative to the Mariana Trench? These seamounts are located to the north or northwest of the Mariana Trench and Challenger Deep. 2. What are the depths below sea level for each of the placemarked serpentinite seamounts: Yinazao, Asut Tesoru, and Fantangisna? The summit of Yinazao is approximately 10,800 feet below sea level. The top of the Asut Tesoru Seamount is about 4,200 feet below sea level. As a submarine volcano, its topography may change with volcanic activity. The summit of Fantangisna Seamount is approximately 5,900 feet below sea level. These depths represent the 2 Before you begin Part 1, log in to Canvas and open this Activity. You will see one .kmz file. Click on it and it will download. Click on the downloaded .kmz file to open Google Earth and import the files. If you did not save the Smithsonian Global Volcanism from the Plate Tectonics exercise, use Google or another search engine to find “smithsonial global volcanism network google earth placemark file” and click on the .kmz file that indicates it contains global (or world) volcanoes. Once it downloads, click on the .kmz file to open it in Google Earth. Then, drag and drop it to your “My Places” file. Tips: Use Google or another search engine to find images or maps for the Mariana Trench if you don’t know how to locate it. To get accurate readings of the seamount summit areas, zoom in close.

Introduction to Earth Science 08 GeoMapApp & Google Earth Exploration of Mariana Subduction Zone 3. Given your answer to question 2 above, what is happening in the Mariana Trough, and why isn’t the West Mariana Ridge still part of the active arc? The Mariana Trough is a back-arc basin formed due to extensional forces that pull the overriding plate apart, leading to seafloor spreading and the creation of new oceanic crust. The West Mariana Ridge was once part of the active arc, but as the tectonic regime shifted to back- arc spreading, the ridge became separated and now represents a remnant of the former volcanic arc system. 4

Introduction to Earth Science 08 GeoMapApp & Google Earth Exploration of Mariana Subduction Zone Part 3: Comparing Google Earth and GeoMapApp Images A. By comparing the Google Earth and GeoMapApp images, find the four serpentinite seamounts visited during Expedition 366 on GeoMapApp. Question: 1. Looking at the Google Earth and/or GeoMapApp image, are these the ONLY serpentinite seamounts in the Mariana fore-arc region (the region between the Mariana arc and the Mariana Trench)? How many others can you see that might be like them (give a number)? Conical Seamount is another serpentinite seamount. Part 4. Finding the Challenger Deep in GeoMapApp A. The deepest spot in the Mariana Trench is known as the Challenger Deep. It is over 11km (about 37,000 feet) deep! Use the Distance/Profile tool in GeoMapApp to find the Challenger Deep, or the elevations data in Google Earth (be sure Terrain is turned on!). Question: 2. When you have found the Challenger Deep, take a screen capture on your computer showing the profile line on the map and the profile graph. Paste that picture as the answer. 5 Tip: The Google Earth placemarks include the seamounts’ latitudes and longitudes. Tip: The Distance/Profile tool is an icon in the menu of GeoMapApp (it looks like a mountain). Once you click on this, it will take a moment for the GMRT Grid (the proper Digital Elevation Model, DEM, that underlies GeoMapApp) to load. After the GMRT Grid has loaded, you can draw a line with the cursor anywhere on the map, and a profile graph will appear. The profile graph is a plot of depth in meters (on the vertical axis) versus distance in kilometers (on the horizontal axis) and it shows the shape of the topography along a line segment between two points. Make profiles by drawing line segments along the Mariana arc and look at the plots. Find the profile with the deepest depth and that’s the Challenger Deep (remember, it is over 11km deep).