Earth Science: The Atmosphere

Atmosphere

• Comprises the layer where humans live; most weather occurs here.
• Extends over 560 km above Earth's surface.
• Chemical composition: approximately 78% Nitrogen, 21% Oxygen, 1% other gases.
• Divided into five layers: Exosphere, Thermosphere, Mesosphere, Stratosphere, Troposphere.

Exosphere

• Considered the "final frontier" of Earth's atmosphere; air is constantly escaping into space.

Thermosphere

• Absorbs high-energy X-rays and UV radiation from the Sun.

Mesosphere

• Coldest layer of the atmosphere, with temperatures around -90°C (-130°F); most meteors burn up here.

Stratosphere

• Contains the ozone layer, extending from the top of the troposphere to about 50 km above ground.

Troposphere

• The lowest atmospheric layer, supporting life and weather patterns.

Geosphere

• Comprises the solid Earth, including both the surface (continental and ocean crust) and interior layers.
• The surface crust is constantly moving.

Crust

• The outermost layer of Earth, mainly composed of silica and light metallic elements.
• Thickness ranges up to 15-20 km.

Lithosphere

• Includes the crust and the upper layer of the mantle.

Mantle

• A molten layer predominantly made of silica, iron, and magnesium.
• Thickness: about 2,900 km.

Core

• Composed of iron and nickel; divided into outer (liquid) and inner (solid) cores.
• Outer core thickness: 2,200 km; inner core thickness: 1,250 km.

Hydrosphere

• Encompasses all forms of water on Earth, including surface water and groundwater.
• Freshwater constitutes 3% of total water, with 70% of that being frozen in glaciers.

Cryosphere

• Refers to Earth's frozen components including snow, glaciers, ice sheets, and permafrost.
• Crucial for the global climate system.

Biosphere

• The "life zone" of Earth, containing all living organisms and organic matter.
• Interacts with three subsystems: atmosphere, hydrosphere, and geosphere.

Food Chain

• Represents the hierarchical structure of biological interactions in the biosphere.

Earth System Interactions

• Continuous flow of matter and energy occurs between hydrosphere, atmosphere, geosphere, and biosphere.

Theories of Origin of the Universe

• Big Bang Theory: Proposed by Georges Lemaitre; universe began from a hot, dense state, expanding rapidly.
• Steady State Theory: Suggests the universe has no beginning and continuously creates new matter.
• Solar Nebula Theory: Describes sun and planets formation from a rotating disk of gas.
• Multiverse Model: Proposes multiple or infinite universes resulting from ongoing inflation.

Key Astronomical Metrics

• Length of solar day (rotation): 23.934 hours.
• Length of year (revolution around the sun): 365.26 days.
• Equatorial inclination to orbit: 23.4393 degrees.

Unique Characteristics of Earth

• Fifth largest planet in the solar system, primarily composed of iron, oxygen, silicon, and magnesium.
• Oblate spheroid shape with a diameter of 13,000 km.
• Average distance from the sun: 149,598,262 km (92,956,050 miles).

Capture Theory

• Explains that the Sun's gravity attracted materials from a protostar, forming protoplanets through collisions.