Earth Science: Earth's Subsystems

Earth's Subsystems

• Earth consists of four interconnected subsystems known as spheres: atmosphere, geosphere, hydrosphere, and biosphere.
• These subsystems overlap and allow for the flow of matter and energy across their boundaries.

Atmosphere

• Extends from the Earth's surface to approximately 10,000 km and is divided into five layers: troposphere, stratosphere, mesosphere, thermosphere, and exosphere.
• Composition: 78.08% nitrogen, 20.95% oxygen, 0.93% argon, and trace gases (0.04%) including greenhouse gases like ozone and carbon dioxide.

Troposphere

• Temperature decreases with altitude; it contains almost all atmospheric water vapor and is where most weather phenomena occur.
• Clouds form when air is saturated with water vapor, cooling to the dew point.

Stratosphere

• Temperature increases with altitude due to the ozone layer absorbing ultraviolet radiation.
• Lacks weather systems and contains rare nacreous clouds which exhibit iridescent colors.

Mesosphere

• Coldest layer; temperature drops as altitude increases, with noctilucent clouds being the highest clouds formed by ice crystals.

Thermosphere

• Free of vapor and cloudless; known for hosting the International Space Station (ISS) at about 408-410 km altitude.
• Includes the ionosphere, which is critical for radio communications.

Exosphere

• Uppermost layer where atmospheric pressure is very low, allowing gas molecules to escape into space.
• Hosts many artificial satellites.

Geosphere

• Refers to the solid parts of Earth, including rocks, minerals, and soils, as well as the Earth's interior and surface features like mountains and beaches.

Hydrosphere

• Encompasses all water in various forms: liquid (rivers, lakes, oceans), vapor (water vapor in the atmosphere), and solid (ice and snow).
• Water serves essential roles in supporting life and maintaining Earth's processes.

Cryosphere

• Represents areas of Earth where water is in solid form, including glaciers, ice caps, sea ice, and permafrost.
• Reflects solar radiation to help maintain the planet's climate.

Biosphere

• The zone of life on Earth, extending from deep soil to the ocean trenches and high mountains.
• Biodiversity is highest in the tropics due to favorable climatic conditions.

Energy and Matter Flow

• Energy flows unidirectionally through ecosystems, primarily entering as sunlight and existing as heat.
• Matter is recycled among the subsystems; essential chemical elements are circulated through biogeochemical cycles.

Biogeochemical Cycles

• Natural pathways through which substances such as water and carbon move between Earth's abiotic (non-living) and biotic (living) components.
• The water cycle illustrates continuous movement of water on the surface, in the atmosphere, and underground.

Specific Cycles Noted

• Water Cycle: Involves evaporation, condensation, and precipitation processes.
• Carbon Cycle: Describes the flow of carbon among the atmosphere, biosphere, and geosphere, playing a crucial role in climate regulation.

Additional Concepts

• Dew forms when moisture condenses at the dew point, and frost occurs at cold temperatures.
• Permafrost is a permanently frozen layer that can influence ecosystems and climate.

These study notes encompass the four spheres of Earth and their interactions, focusing on key concepts and definitions that are vital in understanding Earth science.