# Formation of Iceland How a mantle plume and the Mid\-Atlantic Ridge built Iceland, shown on a cutaway diorama By nimble\-dolphin\-af27b2f7 Topic: Earth & Geography [Open the interactive Jig](https://ask.jig.com/j/6QZyi9kAH5CH) ## Transcript ### 1. Formation of Iceland Iceland is a young island of fire and ice in the North Atlantic\. It sits where two forces meet: a crack in the sea floor and a column of hot rock rising from deep inside the Earth\. Drag the gallery to look around\. Iceland covers about 103,000 square kilometres, and glaciers still cover about a tenth of it\. ### 2. Two plates pulling apart The Mid\-Atlantic Ridge runs straight through Iceland\. West of it is the North American Plate, east of it the Eurasian Plate, and they drift apart about 2 centimetres a year\. Press the button or drag a plate sideways to open the rift\. That is roughly how fast your fingernails grow\. The boundary is a band of volcanic zones, not a single line\. ### 3. Hot rock rising Slice the island open\. Beneath it, a mantle plume of unusually hot rock rises from at least 400 kilometres down and spreads out under the plates\. The rock is solid, but it creeps upward very slowly, like warm wax\. The cross\-section is not to scale: the crust is drawn much thicker than it really is\. ### 4. Melting under the rift Where the plates thin out, the rising rock is under less pressure and part of it melts\. The melt collects in pockets and shallow chambers, then forces its way up through cracks\. Set off a fissure eruption\. Most of Iceland is basalt, the dark rock that forms when this kind of lava cools\. ### 5. Rising from the sea Ocean ridges usually stay deep underwater\. Here the plume supplies so much extra melt that the crust grows up to 40 kilometres thick, and it floats high enough to break the surface\. Slide through the last 30 million years\. The first land rose above the waves about 16 to 18 million years ago\. ### 6. Oldest at the edges New rock forms along the rift and is carried away on both sides\. So the youngest rocks lie in the volcanic zones, and the oldest are in the far west and east\. The colours show rock age, from red near the rift to blue at the coasts\. The oldest rocks above sea level are about 16 million years old, in the Westfjords and the East Fjords\. ### 7. Still growing Iceland is still being built\. Eruptions add new land, and the plates keep pulling it apart\. At Thingvellir you can walk through the rift valley between two continents\. The island of Surtsey rose out of the sea off the south coast in eruptions from 1963 to 1967\.