EARTH'S PLATES AND THEIR MOVEMENTS As we go about our daily lives Earth feels firm beneath our feet It may come as a surprise that Earth is really covered in plates that are slowly moving Earth is covered in a rigid outer layer called the lithosphere Under the lithosphere is a soft layer of melted rock called the asthenosphere The lithosphere is broken up into about a dozen large plates and several small plates These plates move slowly North American Plate Eurasian Plate Eurasian Plate Juan de Fuca Plate Caribbean Plate As you can see from this map Earth's plates are a mix of different sizes and shapes Philippine Plate Cocos Plate Arabian Plate Pacific Plate African do Australian Plate Plate Nazca Plate South American Plate Antarctic Plate Scotia Plate 0 1 500 3 000 miles 0 1 500 3 000 kilometers 2006 Eylepuder
The Himalayas are a mountain range in Asia They were formed by plate movements only about 2 to 4 inches 5 to 10 centimeters per year Think About It Do you think it takes hundreds thousands or millions of years for a mountain to form The movements of these plates have a huge effect on our planet Sudden plate movements can cause earthquakes The movements of the plates can also form mountains and volcanoes Over long spans of time the movement of the plates known as plate tectonics can change the shape of continents and oceans Scientists study plate tectonics to better understand the history of our planet 5
EARTH S LAYERS core 4,300 miles mantle 1,800 miles crust 3 19 miles Earth's surface layer is a crust of solid rock The crust is thinner under the oceans than it is under the continents Under the continents it averages about 19 miles 30 km thick Underneath the crust is the more compact rock of the mantle on which the crust basically floats The mantle is much thicker about 1 800 miles 2 900 km The temperature at the lower part of the mantle is about 6 700°F 3 700°C The rock there is soft and can move slowly Below the mantle is Earth's core 2014 Encyclopaedia Britannica Inc This diagram shows Earth's three layers As you can see the crust is by far the thinnest
ocean oceanic crust continental crust 10 lithosphere rigid rocks The asthenosphere includes parts of the upper mantle It is under the lithosphere and above the lower mantle 100 asthenosphere weaker plastic rocks upper mantle depth km 600 700 lower mantle The outer part of the core is liquid while the center of 500 the core is solid The lithosphere consists of the crust and the rigid upper mantle The asthenosphere is the partially molten zone in the mantle between 60 and 400 miles 100 and 650 km below the surface The tectonic plates slide across the top of the asthenosphere 2 900 VOCABULARY Molten things have been melted often by great heat
