Plate Tectonics and Continental Drift Voc Set 2 Asthenosphere the soft layer of the Earth on which pieces of the lithosphere move; flowing portion of the upper mantle ??? Did you know? The asthenosphere ◦ flows like a liquid ◦ breaks like a solid (sort of like molten glass, but MUCH hotter) Did you know? Temperatures in the asthenosphere: 1400-3000 degrees celsius (the surface of the Sun is about 5000 C) Lithosphere the outermost layer of the Earth, including the crust and uppermost, solid portion of the mantle Did you know? Lithosphere means “ball of stone” in Greek Did you know? The lithosphere is a very thin layer – only about 1000 km (620 miles) thick. Ridge a line or range of hills or mountains, or an elongated elevation on the ocean bottom Did you know? The mid-ocean ridges of the world are all connected to make one long mountain range? It is about 60,000 km long – that’s 37,282 miles! Trench a long, steep-sided valley on the ocean floor that happens when one plate subducts under another Did you know? The oldest ocean floor crust is found at subduction zones, where old crust will be recycled back into magma. Did you know? Trenches are usually found near volcanic island arcs. Examples: Fault a break in the Earth's crust where rocks will slide past each other Did you know? Fault lines are frequent sites of earthquakes. Did you know? Fault lines are frequent sites of earthquakes. Rift Valley a long, deep valley formed by two tectonic plates moving away from each other Did you know? Parts of the East African Rift Valley are called the “cradle of mankind.” The remains of “Lucy,” an early hominid that lived 3.2 million years ago, were found there!