Plate Tectonics

Explore Plate Tectonics with our 6th grade science worksheet! Learn about continental drift and more.

Reading Comprehension In 1912, a scientist named Alfred Wegener noticed that the continents seem to fit together. They look like pieces of a puzzle. Wegener concluded that at one time the continents must have been one big continent. He called this supercontinent Pangaea.Wegener needed evidence to show that his idea was possible. He learned of rocks and fossils in South America that were the same as some rocks and fossils in Africa. This evidence supported his idea that the continents had once been joined. What evidence shows that the continents had once been joined? lakes fossils trees Wegener concluded that the continent Pangaea began to break apart about 200 million years ago. The pieces of Pangaea slowly drifted apart. These pieces make up the continents we know today. Wegener was right about Pangaea and his theory of continental drift. But he didn't know what made the continents drift apart. So other scientists did not believe his ideas.In the 1960s scientists began to study the ocean floor. They found that new ocean crust is made at tall ridges on the ocean floor. Heated rock rises through cracks in the crust. Then it cools, hardens, and makes new ocean floor. As new crust forms, the two sides of the ridge spread apart, or drift. Old ocean crust is destroyed at deep trenches on the ocean floor. This happens when ocean crust is pushed into Earth's hot mantle, where it melts. This is the theory of seafloor spreading. New crust forms at _. beaches ocean trenches ocean ridges Seafloor spreading helps explain continental drift. Earth is like a ball with several different layers. Earth's crust and solid upper mantle form the lithosphere. The lithosphere is broken into huge pieces called tectonic plates. These tectonic plates fit together. When the ocean floor spreads apart, the continents on these plates move apart too.The theory of plate tectonics explains how these huge plates move. The layer of Earth beneath the lithosphere is like a soft plastic. This soft layer of Earth is called the asthenosphere. Hot matter in this layer flows like a liquid. This matter from deep inside Earth flows up toward the crust. There, it cools and sinks toward Earth's core. This up-and-down motion of heated matter is called a convection current. The theory of plate tectonics explains _. how matter inside Earth is heated how tectonic plates move where the lithosphere is Tectonic plates sit on top of the asthenosphere. As convection currents in the asthenosphere move up and down, the tectonic plates also move. Tectonic plates move very slowly—they move only a few centimeters each year. But these small movements can make big things happen over time. How do tectonic plates move? quickly slowly rapidly Tectonic plates can collide, or run into one another. They can spread apart. They can slide past one another. The movement of tectonic plates can cause earthquakes. The movement of tectonic plates can cause earthquakes convection currents tornadoes Word Study Antonymsare words that mean the opposite.For example, large is the opposite of small.Read each sentence and type in the word that means the opposite of the bold word. oceans opposed different join destroyed lower many small hard falls What do the arrows represent? the location of tectonic plates a type of energy the movement of matter the changing shape of the seafloor What causes the pattern shown in the diagram? heat from inside Earth heat from outside Earth energy from the atmosphere friction from moving tectonic plates What is this pattern of rising and sinking matter within the mantle called? continental drift seafloor spreading convection currents