Overview
This lecture introduces the concept of Earth's dynamic interior, exploring its layered structure, composition, and the processes that drive geological activity.
Structure of the Earth
- The Earth is composed of three main layers: the crust, mantle, and core.
- The crust is the Earth's thin outermost layer, ranging from 5-70 km thick.
- The mantle lies beneath the crust, composed of semi-solid rock that moves slowly.
- The core consists of a liquid outer core and a solid inner core, primarily made of iron and nickel.
Characteristics of Each Layer
- The crust is solid and divided into oceanic (dense, basaltic) and continental (less dense, granitic) types.
- The mantle is about 2,900 km thick and is involved in convection currents responsible for plate movement.
- The outer core is liquid and generates the Earth's magnetic field.
- The inner core is solid due to immense pressure, despite high temperatures.
Plate Tectonics and Earth's Dynamics
- The lithosphere includes the crust and uppermost mantle and is broken into tectonic plates.
- Plates move over the asthenosphere, a partially molten layer within the upper mantle.
- Plate movements cause earthquakes, volcanic activity, mountain building, and ocean trench formation.
Importance of Earth's Structure
- Understanding Earth's layers helps explain natural disasters like earthquakes and volcanoes.
- The movement of materials inside Earth is key to the rock cycle and resource distribution.
Key Terms & Definitions
- Crust — Earth's thin, solid outermost shell.
- Mantle — Thick, mostly solid layer beneath the crust with slow-moving rock.
- Core — Central part of Earth, with liquid outer and solid inner layers, mostly iron and nickel.
- Lithosphere — Rigid outer layer made of crust and upper mantle.
- Asthenosphere — Semi-fluid upper mantle layer that allows plate movement.
- Plate tectonics — Theory explaining the movement of Earth's lithospheric plates.
Action Items / Next Steps
- Review textbook section on Earth's interior structure.
- Prepare questions on layers and their properties for next class discussion.