Ciyanna and Summer

The crust is the outermost layer of the Earth, but it is also the thinnest layer of the Earth.

The mantle is the layer of the Earth between the crust and the core. Compared to the crust, the mantle is extremely thick and contains most of the Earth’s mass.

The core extends from the bottom of the mantle to the center of the Earth. Mars is slightly smaller that that of the Earth’s core.

The lithosphere is made of two parts-the crust and the rigid upper part of the mantle. The lithosphere is divided into pieces called tectonic plates.

The asthenosphere (also known as the weak sphere) is a soft layer of the mantle on which pieces of the lithosphere move. It flows at the same rate as your fingernails grow.

The mesosphere is beneath the asthenosphere is the strong, lower part of the mantle. The mesosphere extends from the bottom of the asthenosphere down to the Earth’s core.

The outer core is the liquid layer of the Earth’s core that lies beneath the mantle and surrounds the inner core.

The inner core is the solid, dense center of our planet that extends from the bottom of the outer core to the center of the Earth. The inner core is about 6,738 km beneath the surface.

Tectonic plates are pieces of the lithosphere that move around on top of the asthenosphere. All tectonic plates have names, some of which we already know. Each tectonic plate fits the tectonic plate that surround it.

The continental drift is the theory that continents can drift apart from one another. Scientists think that at one point all seven continents once fit together like a puzzle.

Sea floor spreading is the process by which new oceanic lithosphere is created as older materials are pulled away. As tectonic plates move away from each other, the sea floor spreads apart and magma rises to fill in the gap.

The first section is about how the Earth has three basic compositional layers which are the crust, the mantle, and the core. The Earth is made up of five main structural layers which are the lithosphere, asthenosphere, mesosphere, outer core, and the inner core. The lesson also talks about tectonic plates and how they are large pieces of the lithosphere.

Section 2 is about Wegner’s theory of continental drift and how all of them fit together like a puzzle. Our continents today were originally joined together in the ancient continent Pangaea. This section talks about sea-floor spreading and how it comes from magnetic reversals recorded in the ocean’s floor.