Lesson 2: The Geosphere - Structure of the Geosphere: We learned that the geosphere has three main layers, which differ by their densities. Density is a measure of the mass of the material divided by its volume. The outermost layer of the geosphere is called the crust and is formed of brittle rocks. Oceanic crust is formed mainly of the dense igneous rock basalt and gabbro, which have high levels of iron and magnesium. Then we learned that the continental crust is made of igneous, metamorphic, and sedimentary rocks that are rich in silicon and oxygen. These elements that have a fairly low density therefore the continental crust is less dense than oceanic crust.
Earth’s core is the dense, metallic center of Earth.
Discussion Question: How do Earth systems interact to cause the formation of soil?
The rocks of the geosphere interact with the hydrosphere and the biosphere as the rocks are subject to chemical and physical weathering at and beneath Earth’s surface. As the rock material breaks down into finer sediments, it mixes with organic material from the decay of plants and animals; closer to the surface, the movement of plants and animals through the soil creates open spaces for air from the atmosphere to enter and mix with the soil. The soil also serves as a reservoir for different materials, including carbon, phosphorus, and water, which cycle through the geosphere.