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Unit: Earth geological and climatic history

How do we know what the Earth is made up of? Has someone dug to the core? No, but we humans have been able to see how earthquake (seismic) waves have been bent and reflected through our planet to get a reasonable idea of what is down there.

About this unit

What is the Earth made up of and how do we know? What causes the seasons? Are there longer-ranging cycles in Earth's climate?