Earth's Structure and Atmosphere

• The Earth's structure is divided into layers based on chemical composition and physical properties.

Chemical Composition Layers

• The core is the innermost layer made of iron and nickel.
• The mantle surrounds the core, composed of silicate rocks rich in iron and magnesium.
• The crust is the outermost layer composed of light silicate rocks.

Physical Property Layers

• The lithosphere is the rigid outermost layer, consisting of the crust and the uppermost part of the mantle.
• The asthenosphere is a partially molten, ductile layer within the upper mantle on which the lithosphere floats.
• The mesosphere is the solid lower mantle, more rigid than the asthenosphere due to higher pressure.
• The outer core is liquid because of high temperatures, facilitating convective flow.
• The inner core is solid due to immense pressure, despite high temperature.

The Atmosphere

• The atmosphere is the layer of gases that surrounds Earth held in place by gravity.
• It primarily consists of nitrogen (about 78%) and oxygen (about 21%), along with argon, carbon dioxide, and smaller amounts of other trace gases.
• The atmosphere protects life on Earth by absorbing harmful ultraviolet (UV) radiation from the sun and moderating temperature extremes between day and night.

Atmospheric Layers

• The troposphere is the lowest layer, where weather occurs, and temperature decreases with altitude.
• The stratosphere, above the troposphere, contains the ozone layer that absorbs UV radiation; temperature increases with altitude.
• The mesosphere is above the stratosphere, where temperature decreases with altitude, and meteors burn up.
• The thermosphere is above the mesosphere, where temperature increases with altitude due to absorption of high-energy solar radiation.
• The exosphere is the outermost layer and fades into space.

Atmospheric Processes

• Solar radiation heats Earth's surface, which then heats the atmosphere from below.
• Convection, conduction, and radiation transfer heat within the atmosphere.
• The Coriolis effect, caused by Earth's rotation, deflects moving air and influences wind patterns.
• Greenhouse gases, such as carbon dioxide, methane, and water vapor, trap heat in the atmosphere, contributing to the greenhouse effect and global warming.

The Hydrosphere

• The hydrosphere includes all water on Earth, in liquid, solid (ice), and gaseous (water vapor) forms.
• It encompasses oceans, seas, lakes, rivers, groundwater, ice caps, glaciers, and atmospheric moisture.
• Oceans cover about 71% of Earth's surface and contain approximately 97% of Earth's water.

The Water Cycle

• Evaporation is the process by which liquid water turns into water vapor and enters the atmosphere.
• Transpiration is the release of water vapor from plants into the atmosphere.
• Condensation is the process by which water vapor turns into liquid water, forming clouds.
• Precipitation is water falling back to Earth as rain, snow, sleet, or hail.
• Runoff is water flowing over the land surface, eventually reaching streams, rivers, and oceans.
• Infiltration is water soaking into the ground, replenishing groundwater supplies.

Importance of the Hydrosphere

• Water is essential for all known forms of life.
• It regulates Earth's climate by absorbing and distributing heat.
• It shapes Earth's surface through erosion and weathering.
• It is used for drinking, agriculture, industry, and transportation.

The Lithosphere

• The lithosphere is the rigid outer layer of Earth, consisting of the crust and the uppermost part of the mantle.
• It is divided into tectonic plates that move and interact, causing earthquakes, volcanic activity, and mountain formation.

Composition of the Crust

• Continental crust is thicker but less dense than oceanic crust, primarily composed of granite.
• Oceanic crust is thinner and denser than continental crust, mainly composed of basalt.
• The crust consists of various rocks and minerals, including silicates, oxides, and carbonates.

Plate Tectonics

• Plate boundaries are where tectonic plates interact and are classified as divergent, convergent, or transform.
• Divergent boundaries are where plates move apart, creating new crust, such as at mid-ocean ridges.
• Convergent boundaries are where plates collide, resulting in subduction, where one plate slides beneath another, or mountain building.
• Transform boundaries are where plates slide past each other horizontally, causing earthquakes, such as the San Andreas Fault.

Geological Processes

• Weathering is the breakdown of rocks and minerals at Earth's surface, either physically (mechanical) or chemically.
• Erosion is the removal and transport of weathered material by wind, water, ice, or gravity.
• Deposition is the settling of transported material in a new location, forming sediments.
• Volcanism is the eruption of molten rock (magma) onto Earth's surface, creating volcanoes and lava flows.
• Earthquakes are sudden releases of energy in Earth's lithosphere, causing ground shaking and seismic waves.