Geo 1045 Sg 8 Oceans and Coasts

Tsunami Generation

Displacement of large water volumes by subduction zone earthquakes, underwater landslides, volcanic eruptions.

Signs of Tsunami

Rapid recession of water, exposed sea floor, loud roaring noise.

Tsunamis vs. Wind-Driven Waves

Tsunamis have longer wavelengths (>100 km) and travel faster (up to 700 km/h); wind waves are much smaller and slower.

Tsunamis vs. Wind-Driven Waves

Tsunamis have longer wavelengths (>100 km) and travel faster (up to 700 km/h); wind waves are much smaller and slower.

Destructive Nature of Tsunamis

Massive volume and high momentum allow deep inland penetration and widespread devastation.

Hurricane Formation

Requires sea surface temperatures >26.5°C (80°F), low wind shear, and moist air in the mid-troposphere.

Hurricane Structure

• Eye (calm)

• Eyewall (intense winds)

• Rainbands (spiraling bands of heavy rain).

Hurricane Destruction

High winds, storm surge (sea level rise), heavy inland flooding.

Coral Bleaching Cause

Stress (especially heat stress) causes coral to expel symbiotic algae (zooxanthellae), leading to whitening and often death.

Wind-Driven Waves

Formed by friction between wind and surface water; characterized by crest, trough, wavelength, and wave height.

Coastal Erosion

Driven by wave energy, currents, storms, and rising sea levels.

Beach Protection Measures

Seawalls, groins, breakwaters; can cause downdrift erosion, reducing sediment supply.

Negative effects of Seawalls

Negative effects of Beach Groins

Negative effects of breakwaters

Coastal Wetlands

Marshes and mangroves that buffer coasts against storms and provide vital ecosystems.

Emergent vs. Submergent Coasts

• Emergent: Uplifted by tectonics or glacial rebound.

• Submergent: Drowned by rising sea levels or land subsidence.

Processes Leading to Coastline Changes

Tectonic uplift/subsidence, sea-level changes (eustatic, isostatic).

Beach Sediment Budget

Balance between sediment input (rivers, cliff erosion) and output (longshore drift, storms).

Dam Effects

Trap sediments upstream, starving coastal beaches of replenishment material.

Width of Intertidal Zone

Determined by tidal range, wave energy, and slope of coastal profile.

Coastal Material Types

Sandy beaches (mobile, dynamic), rocky coasts (resistant to erosion), muddy coasts (fine sediments, low energy environments).