3. Journey Through Earth - Background

Teacher Background
The earth is composed of many distinct layers. Their identity has primarily been inferred from seismic data and from analysis of the magma welling up out of volcanoes. A table of the various layers and a brief description of each follows (this same information is provided on the Earth Journey Teacher Cheat Sheet).

Layer Actual dist. from center  Description
Inner core 

0-1200 km

(6400-5200 km from surface) 

Metal (iron and nickel)
3-5 million atmospheres of pressure
Solid – Even though the temperatures are tremendous, the pressure is also so tremendous that the inner core is squeezed into a solid state.
Outer core

1200-3500 km

(5200-2900 km from surface) 

Metal (iron and nickel)
1-2 million atmospheres of pressure
Liquid – Since there’s less pressure, the outer core can flow as a liquid and its motion is thought to generate Earth’s magnetic field.

3500-6300 km

(2900-100 km from surface) 

Rock (magma)
1 million atmospheres of pressure
Near-solid to liquid – Near the core, the mantle is a plastic solid, meaning that it is a liquid but it incredibly viscous and flows incredibly slowly. It becomes more liquid and less viscous as you move outward and the pressure decreases.
Lithosphere and crust

6300-6400 km

(100-0 km from surface) 

Rock and ocean
Very low temperature and pressure
Solid (except for the ocean)
The lithosphere forms the tectonic plates. The bottom of the lithosphere is technically still part of the mantle. Riding on top of the lithosphere is the crust, the layer we live on (between 5-70 km deep).

I structured the walk for 640 m since the calculations become very easy from the actual distances to the walk distance (and thus is easy for kids to see the relationship). In addition, if the 640 m walk is arranged in a loop, it is quite easy to fit the walk into a regular 45-50 minute period.

Student Prerequisites