Above is a clickable image showing the layout of earth’s tectonic plates, as scientists have them outlined today. Plate margins are the edges of the plates, where all the awesome power of nature is released in earthquakes and volcanoes! To go back to the page you were just reading, click on that part of the map. To find out more about each of the three types of plate boundaries, click on them!

A spreading boundary is where the tectonic plates are separating. Some spreading

boundaries are places where the crust is sinking downward as it is stretched thin - like in the East Rift Valley of Africa, where the Dead Sea is located (see Figure 1, at right). As you can see in the above map, many of the spreading boundaries are located deep in the ocean on the sea floor. These are places where volcanic activity is at a premium because the crust is being torn open (as in splitting and cracking, like an egg breaking open). New crust is forming when molten lava from deep down oozes out of the cracks where the plates are coming apart (see Figure 2). Long chains of undersea mounts (the world’s longest is the mid-Atlantic Ocean Ridge) and Volcanic islands typically characterize these type of plate margins.

A converging boundary is the opposite of a spreading boundary. Typically you will see a converging boundary on a tectonic plate that is on the opposite side of a spreading boundary - of course! As a plate moves in one direction it collides with the adjacent plate on its “front” end, while the trailing end of the plate is being pulled and stretched (spreading) from the plate on the other end. For example, look at the Pacific plate. The entire plate is moving north and westward (up and to the left) as the top edge converges with the North American and European plates. You can see the left side of the Pacific plate is converging with the Indian plate. Then if you look at the bottom and right edges of the plate you can see it’s spreading apart from the Antarctic and Nazca plates.

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