What is inside Earth? Because Earth’s center is too deep to dig to, we gather clues by looking at earthquakes, volcanoes, deep-sea trenches and mountains.

Physical Structure of the Earth (5 Layers) Lithosphere- rigid outer layer (crust) Asthenosphere- solid rock that flows slowly (like hot asphalt) Mesosphere- middle layer (Mantle) Outer Core- liquid layer Inner Core- solid, very dense

Using Volcanoes and Earthquakes Volcano give clues to what is inside the planet and what it is made of. When an earthquake happens, a seismograph measures the waves all over the world. These waves come at different frequencies and are “bent”, which tells scientists that Earth is made of layers that have different thickness and physical properties.

Crust Continental crust and Oceanic crust Continental crust is less dense than oceanic crust, though it is considerably thicker; mostly 35 to 40 km versus the average oceanic thickness of around 7-10 km.

The oceanic crust consists of a volcanic lava rock called basalt The oceanic crust consists of a volcanic lava rock called basalt. The continental crust is composed mostly of granite.

The Mantle Largest layer of the Earth3000 km or1800 miles thick. The temperature of the mantle varies from 1600 degrees Fahrenheit at the top to about 4000 degrees Fahrenheit near the bottom! Plastic like layer.

Outer Core The outer core is so hot that the metals in it are all liquid state. The outer core is located about 1800 miles beneath the crust and is about 1400 miles thick.

Inner Core The inner core of the Earth has temperatures and pressures so great that the metals are squeezed together and are not able to move about like a liquid, but are forced to vibrate in place as a solid. The inner core is made of nickel and iron. The inner core begins about 4000 miles beneath the crust and is about 800 miles thick.

Inner Core The temperatures may reach 9000 degrees F and the pressures are 45,000,000 pounds per square inch. This is 3,000,000 times the air pressure at sea level! Hot Hot!

Continental Drift Alfred Wegener’s theory stated that Pangaea was once one continent that slowly broke apart and moved to it’s current position we now have. Wegener called this the theory of continental drift – the movement of continents.

Pangaea In 1912, scientist Alfred Wegener proposed the idea of a supercontinent named Pangaea. He looked at a map and noticed the continents could fit together like a puzzle.

Clues to support Continental Drift Wegener found fossils, such as the plant fossil Glossopteris, in Africa, South America, Antarctica, and Australia. Fossils of the reptile Mesosaurus were found in Africa and South America. These were freshwater and land animal, so it is unlikely they swam across the ocean. Wegener also found fossils in cold, icy Antarctica of organisms that live in warm, tropical climates.

Plates

Convection Currents Convection currents are caused by the very hot material at the deepest part of the mantle to rise. While the coldest and densest material sinks.

Convection Currents

PLATES IN MOTION A divergent plate movement occurs when two plates move away from each other Divergent takes place at the boundary of the oceanic plates and forms new sea floor. This process is called sea-floor spreading.