Earth’s Surface and Internal Processes
Earth’s Surface Processes
Weathering
Weathering is the alteration of rocks and minerals on Earth’s surface due to atmospheric agents. There are three types of weathering:
- Physical/Mechanical Weathering: Common in extreme climates (e.g., cold deserts) with minimal liquid water. Examples include frost wedging, thermal expansion and contraction, salt crystallization, and root action.
- Chemical Weathering: Involves chemical reactions between rock and fluids, prevalent in wet areas.
- Biological Weathering: Caused by living organisms.
Landslides
Causes of Landslides
Landslides are caused by intrinsic factors (lithology, structure, hydrogeological properties) and external factors (earthquakes, rain, snowmelt).
Human Factors Intensifying Landslides
Human activities can trigger landslides by altering slope stability through static loads (construction), dynamic loads (blasting), and changes in slope geometry.
Landslide Prevention and Mitigation
Preventive measures include non-structural (spatial planning, risk mapping) and structural (drainage, slope flattening) approaches. Instrumentation can protect structures in limited areas.
Coastal Modeling
Erosive Forms
Coastal modeling is driven by mechanical action (waves, currents, tides) and chemical action of seawater. Erosion creates features like cliffs and abrasion platforms.
Accumulation Forms
Transport mechanisms include waves, tides, and longshore currents. Accumulation forms include dunes, beaches, coves, bays, estuaries, bars, barrier islands, deltas, tidal flats, lagoons, and marshes.
Earth’s Internal Processes
Earth’s Internal Structure
Earth’s interior is divided into seven zones: crust, upper mantle, transition zone, lower mantle, outer core, and inner core, separated by major discontinuities (Mohorovičić, Gutenberg, Lehman).
Discontinuities
Discontinuities indicate changes in composition, density, pressure, and temperature with depth, detected by variations in P-wave and S-wave velocities.
Seismic Waves
Seismic waves are categorized by particle oscillation:
- P-waves (Primary/Longitudinal): Fastest waves.
- S-waves (Secondary/Transverse): Slower than P-waves.
- L-waves (Surface Waves): High amplitude, low frequency waves traveling along Earth’s surface.
Earthquakes
Origin and Causes
Earthquakes result from the fracturing of rigid rocks within Earth (faults), releasing energy as seismic waves. These waves propagate from the hypocenter to the epicenter on the surface.
Intensity vs. Magnitude
Earthquake intensity measures destructive effects (Mercalli scale), while magnitude measures energy released (Richter scale).