U.S. Department of the InteriorU.S. Geological Survey
Plate Tectonics Mapping
Presenter
Presentation Notes
Plate Tectonics Mapping
ContinentalCrust
Oceanic Crust
Oceanic Crust
Alaska
AleutianTrench
Presenter
Presentation Notes
Subduction processes during plate convergence result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes typically are strung out in chains called island arcs, such as the Aleutian Arc (and associated Aleutian Trench). As the name implies, volcanic island arcs, which closely parallel the trenches, are generally curved. The trenches are the key to understanding how island arcs such as the Marianas and the Aleutian Islands have formed and why they experience numerous strong earthquakes. Magmas that form island arcs are produced by the partial melting of the descending plate and/or the overlying oceanic lithosphere. The descending plate also provides a source of stress as the two plates interact, leading to frequent moderate to strong earthquakes. (from USGS and the Smithsonian Institute’s This Dynamic Earth http://pubs.usgs.gov/gip/dynamic/dynamic.html)��
Presenter
Presentation Notes
17 plate pieces outline
Presenter
Presentation Notes
Subduction processes during plate convergence result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes typically are strung out in chains called island arcs, such as the Aleutian Arc (and associated Aleutian Trench). As the name implies, volcanic island arcs, which closely parallel the trenches, are generally curved. The trenches are the key to understanding how island arcs such as the Marianas and the Aleutian Islands have formed and why they experience numerous strong earthquakes. Magmas that form island arcs are produced by the partial melting of the descending plate and/or the overlying oceanic lithosphere. The descending plate also provides a source of stress as the two plates interact, leading to frequent moderate to strong earthquakes. (from USGS and the Smithsonian Institute’s This Dynamic Earth http://pubs.usgs.gov/gip/dynamic/dynamic.html)
ContinentalCrust
Oceanic Crust
Oceanic Crust
Alaska
AleutianTrench
Presenter
Presentation Notes
Subduction processes during plate convergence result in the formation of volcanoes. Over millions of years, the erupted lava and volcanic debris pile up on the ocean floor until a submarine volcano rises above sea level to form an island volcano. Such volcanoes typically are strung out in chains called island arcs, such as the Aleutian Arc (and associated Aleutian Trench). As the name implies, volcanic island arcs, which closely parallel the trenches, are generally curved. The trenches are the key to understanding how island arcs such as the Marianas and the Aleutian Islands have formed and why they experience numerous strong earthquakes. Magmas that form island arcs are produced by the partial melting of the descending plate and/or the overlying oceanic lithosphere. The descending plate also provides a source of stress as the two plates interact, leading to frequent moderate to strong earthquakes. (from USGS and the Smithsonian Institute’s This Dynamic Earth http://pubs.usgs.gov/gip/dynamic/dynamic.html)��
U.S. Department of the InteriorU.S. Geological Survey
Earthquake Mapping
Presenter
Presentation Notes
Earthquake Mapping
Divergent Convergent Transform
SouthAmerican
Plate
AmericanPlate
PacificPlate
AfricanPlate
EurasianPlate
Indo-AustralianPlate
Antarctic Plate
Eurasian
Plate
NazcaPlate
CocosPlate
PhilippinePlate
ScotiaPlate
CaribbeanPlate
"Teeth" onOverriding Plate
Juan deFuca Plate
North
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SanAndreasFault
S = Shallow (< 40 miles) M = Intermediate (40 - 200 miles) D = Deep (> 200 miles)
Hawaii
Presenter
Presentation Notes
Generally, the depth of an earthquake is related to the type of tectonic boundary in which it occurs. Relatively shallow earthquakes occur at divergent and transform boundaries and hotspots. Closely spaced earthquakes with a range of depths that deepen in the direction of plate movement can reflect a subducting plate at a convergent boundary. Plotting the location and depth of earthquakes in a latitude and longitude area can illustrate a rough outline of the plate boundaries of the Earth and the type of plate boundary in which they occur. Modified from Lillie, 2005.
180˚
170˚W
160˚W 150˚W 140˚W
130˚W
50˚N
55˚N
60˚N
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70˚N
0 500km
020406080
100120140160180200
dept
h in
km
0 100 200 300 400 500 600 700
distance in km
-10-30 km
30-100 km
100-150 km
150-300 km
Depth
NW SE
Presenter
Presentation Notes
The above figures show earthquakes in Alaska greater than or equal to M2 (magnitude 2) recorded between 1970 and 2008. The cross section above is taken across the subduction zone in south-central Alaska and is represented by the dashed line. The colors of earthquake locations represent the depth of the earthquakes as noted on the map. Figure modified courtesy of Lea Burris, Alaska Earthquake Information Center.
