Earthquakes are clues to plate boundaries
Plate movements were first studied using seismographs to study earthquake patterns. They recorded earthquakes caused by the crustal plates moving around the Earth. Scientists found the earthquakes occur along narrow bands on the Earth's surface. These narrow bands of earthquakes outline the major and minor plates here on Earth.
Earthquakes outlining crustal plates, USGS
Tracking moving plates
Today scientists use GPS to track moving plates. GPS sensors are placed around the Earth and are tracked by satellites. Sensors on both sides of the San Andreas Fault give precise measurements of movement by the North American Plate and the Pacific Plate.
Stress on San Andreas Fault
Scientists are concerned about the build up in stress on the rocks in the southern section of the San Andreas Fault and are hoping to use the GPS tracking devices and seismographs to help predict major earthquakes before they occur.
Iceland on Mid-Atlantic Ridge
Iceland sits atop the Mid Atlantic Ridge offering a perfect place for scientists to study a plate movements on a divergent plate boundary. Near the Iceland volcano Krafta fissures form as the island is splitting apart because the North American Plate and the Eurasian Plate are separating.
Rift valleys on Iceland
A rift valley is located right through the center of Iceland. Rifting is when the land is pulling apart and the ground rises and cracks as molten rock moves upward toward a volcano vent.
Eruptions on the island
The ground above molten rock will drop down as a volcanic eruption begins and lava flows out the volcano's vent creating new basalt rocks on the island. Rifting between 1975 and 1984 caused the land to pull apart more than 21 feet (7 meters) in Iceland.
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