Before beginning this lesson, students should be familiar with the layers of Earth's interior. Although we are unable to study the Earth's interior directly, scientists have studied the interior indirectly using seismic waves. The inner core is a solid sphere of dense metals, while the outer core is liquid metal. The cores are composed of mostly iron and nickel. The convection currents within the outer core create Earth's magnetic field. The layer surrounding the outer core is called the mantle, which consists of extremely hot rock. The upper part of the mantle is called the asthenosphere, this part of the mantle flows very slowly in convection currents. Above the asthenosphere, is the lithosphere, the brittle, rigid part of Earth's crust. The lithosphere is separated into tectonic plates which float slowly on the asthenosphere.
Students should also be familiar with the concept of convection currents. Convection currents occur when a heat source is applied to a fluid substance. In Earth's interior, energy from the outer core heats the rock of the mantle, causing it to become less dense. This hot rock rises towards the lithosphere, where it cools, becomes denser, and sinks back towards the outer core. Although the convection currents in the mantle are very slow, they cause plate movements over millions of years.
This video clip describes how scientists used indirect methods to discover the interior composition of Earth and describes where Earth's internal energy originates.
"100 Greatest Discoveries: The Core of Earth" from the Science Channel-2:39 Minutes
The assessment portion of this lesson will include questions relating to the control and experimental groups of the lab activity. Students will need to be familiar with the terms control and variables.
Control: This is the trial the scientist performs before testing any variables.
Variables: The factor the scientist changes between tests.