Earth's Structure and Layers

Structure of the Earth

• The Earth's outermost layer is the crust, divided into continental crust (thicker and less dense) and oceanic crust (thinner and more dense).
• The mantle is the layer below the crust, extending to about 2,900 km deep, and is composed of silicate rocks rich in magnesium and iron.
• The Earth's core comprises the outer core (liquid, mostly iron and nickel) and the inner core (solid, primarily iron).
• The Mohorovičić Discontinuity (Moho) marks the boundary between the Earth's crust and the mantle, with a sudden increase in seismic wave velocities.
• The Gutenberg Discontinuity marks the boundary between the mantle and the outer core, with a significant decrease in seismic wave velocities.
• The Lehmann Discontinuity marks the boundary between the outer core and the inner core, with an increase in seismic wave velocities.

Plate Tectonics

• The lithosphere is the rigid outer layer of the Earth, broken into tectonic plates.
• The asthenosphere is the semi-fluid layer beneath the lithosphere on which tectonic plates move.
• Divergent boundaries are where plates move apart, such as at the Mid-Atlantic Ridge.
• Convergent boundaries are where plates move towards each other, such as at the Himalayas.
• Transform boundaries are where plates slide past each other, such as at the San Andreas Fault.

Major Landforms

• Mountains are elevated areas formed by tectonic forces, such as the Himalayas.
• Valleys are low areas between mountains or hills, often with rivers.
• Plateaus are elevated flat areas.
• Plains are broad, flat, or gently rolling areas.
• Deserts are dry areas with sparse vegetation, such as the Sahara Desert.
• Coastal landforms include beaches, cliffs, and dunes.

Hydrosphere

• Oceans cover about 71% of the Earth's surface.
• The major oceans are the Pacific, Atlantic, Indian, Southern, and Arctic.
• Rivers are large natural streams of water flowing towards oceans, seas, or lakes, such as the Amazon and Nile.
• Lakes are inland bodies of water, such as Lake Superior and the Caspian Sea.
• Glaciers are large ice masses that move slowly over land, such as the Greenland Ice Sheet.

Atmosphere

• The troposphere is the lowest layer of the atmosphere, where weather occurs.
• The stratosphere contains the ozone layer.
• The mesosphere is where meteors burn up.
• The thermosphere is where auroras occur and contains the ionosphere.
• The exosphere is the outermost layer, merging into space.
• The tropopause marks the boundary between the troposphere and the stratosphere.
• The stratopause marks the boundary between the stratosphere and the mesosphere.
• The mesopause marks the boundary between the mesosphere and the thermosphere, and is the coldest point in the atmosphere.
• The thermopause marks the boundary between the thermosphere and the exosphere.

Climate and Weather

• Climate zones include tropical, temperate, and polar regions.
• Tropical climates are near the equator, warm year-round.
• Temperate climates have moderate temperatures, with distinct seasons.
• Polar climates are near the poles, cold year-round.
• Cyclones are large-scale air masses that rotate around a strong center of low atmospheric pressure.
• Tornadoes are violently rotating columns of air in contact with both the surface of the Earth and a cumulonimbus cloud.
• Hurricanes are intense tropical storms with powerful winds and heavy rain.

Biosphere

• Biomes are large regions characterized by specific climate, flora, and fauna, such as rainforests, deserts, and tundras.
• Ecosystems are communities of living organisms interacting with their physical environment.
• Biodiversity is the variety of life on Earth, crucial for ecosystem stability and resilience.