CHAPTER 11 Focus Points
11.1 Earth Formation
Formation of the solar system: The solar system, including Earth, was formed by the coalescence of dust and gas.
Formation of the atmosphere and oceans: Earth’s atmosphere and oceans were formed from gases emitted by volcanoes early in Earth’s history.
11.2 Deep History: Geologic Time
The geologic time scale: Earth is 4.6 billion years old. Its history is divided into epochs, periods, eras, and eons based on major geologic events that occurred in the past.
Uniformitarianism: Earth’s physical systems operate mostly under gradual changes that accumulated over geologic time.
Absolute and relative age: Relative age accounts for the order of events. Absolute age provides the specific age of an object.
11.3 Anatomy of a Planet: Earth’s Internal Structure
Earth’s interior: Earth’s interior is hot and under enormous pressure.
Earth’s interior layers: Earth is composed of three main layers: the core, the mantle, and the lithosphere.
Thickness of the crust: The Moho, which marks the base of Earth’s crust, is deepest beneath high mountains and shallowest beneath the oceans.
Lithospheric plate movement: Convection in the mantle drives the movement of lithospheric plates and creates surface topography.
11.4 Geographic Perspectives: Earth’s Heat and the Biosphere
Earth’s internal heat energy created and maintains Earth’s life-