Earth and Habitable Conditions

Earth

• Estimated 8.7 million different life forms exist, making Earth the only living planet in the solar system.
• Contains about 70% liquid water, crucial for life.
• Classified as a rocky, terrestrial planet with a solid, active surface.
• Earth and Venus maintain sufficient atmospheres due to their size.

Factors That Make a Planet Habitable

• Temperature: Life requires a temperature range from -15°C to 115°C, where liquid water can exist.
• Atmosphere: Earth’s atmosphere is 10 miles thick, keeping surface temperatures warm and shielding from radiation.
• Energy: Cells need a steady supply of light or chemical energy for vital chemical reactions.
• Nutrients: Water cycles and volcanic activity help transport essential chemicals for organisms.

Subsystems of Earth

• Biosphere: Comprises all living entities, including humans and wildlife.
• Hydrosphere: All water, including oceans, lakes, and rivers.
• Lithosphere/Geosphere: Solid components of Earth, including rocks, soils, and minerals.
• Atmosphere: The gaseous layer that insulates and protects the Earth while influencing weather and climate.

Minerals

• Defined as naturally occurring, inorganic solids with a crystalline structure and specific chemical composition.

Properties of Minerals

• Cleavage: Ability to break along specific planes, resulting in smooth surfaces.
• Hardness: Resistance to abrasion measured on the Mohs scale from 1 (softest) to 10 (hardest).
• Luster: Quality of reflected light from the mineral's surface.
• Streak: Color of a mineral powder, which can vary due to impurities.
• Crystal Form: The external shape that reflects the internal atomic structure of the mineral.

Characteristics of Minerals

• Inorganic, with never having been alive.
• Consistent chemical composition unique to the mineral.
• Naturally occurring in the environment.
• Consist of a crystalline structure.
• Solid, not liquid or gas.

Rocks

• Composed of one or more minerals, typically found in mixtures.

Types of Rocks

• Igneous Rocks: Formed from cooled lava or magma.
  • Extrusive (fine-grained, quick cooling from lava).
  • Intrusive (coarse-grained, slow cooling beneath the surface).
• Sedimentary Rocks: Formed from layers of sediments, providing geological history.
• Metamorphic Rocks: Arise from existing rocks altered by heat and pressure.

Exogenic Processes

• Weathering: Breakdown and alteration of rocks through:
  • Physical Weathering: Caused by temperature changes, frost wedging, organic activity, human activities, and abrasion.
  • Chemical Weathering: Includes dissolution, hydrolysis, and oxidation processes.
• Erosion: Involves transportation of materials by agents like wind, water, or ice.

Endogenic Processes

• Heat Transfer:
  • Conduction: Transfer of heat via collisions of atoms.
  • Convection: Movement of heat in fluids, such as the mantle.
• Melting Processes:
  • Decompression Melting: Pressure reduction leads to melting of mantle rocks.
  • Partial Melting: Involves addition of volatiles, increased temperature, or decreased pressure to generate magma.

Metamorphism

• Examples include slate and gneiss as foliated rocks, while non-foliated rocks result from contact metamorphism.

Geological Concepts

• Convergent Boundaries: Create landforms like volcanic arcs.
• Divergent Boundaries: Lead to oceanic lithosphere formation.
• Angular Unconformity: Involves erosion, folding, and marine regression.

Dating Techniques

• Absolute Dating: Determines the year or range of years using radioactive isotopes.
• Relative Dating: Establishes chronological order through rock positioning.
• Principle of Horizontality: Sediments layer in horizontal formations, which aids dating.

Geological Time Scale

• Divisions include periods, epochs, and eras.
• Paleozoic Era: Known as "the age of fish."
• Mesozoic Era: Fossils of dinosaurs and early mammals found from this period.

Natural Hazards

• Include earthquakes, hurricanes, and tsunamis.
• Liquefaction: A hazard that can lead to structural failures in buildings and infrastructure.

Risk and Mitigation

• Regions like Camiguin are high-risk for volcanic eruptions; landslides prone areas include Cebu, La Union, and Mountain Province.
• The Ring of Fire indicates high seismic and volcanic activity.
• Coastal processes such as storm surges and tides contribute to sea-level rise influenced by lunar gravity.
• Mitigation: Actions to reduce long-term risks and hazards in coastal areas.