Natural Disasters: Earthquakes, Landslides, Sinkholes

Earthquakes

• A sudden shaking of the ground caused by the release of energy along geological faults or tectonic plate boundaries.
• The epicenter is the point on the Earth's surface directly above where an earthquake starts.
• The 1994 Northridge earthquake in California had a magnitude of 6.7, resulted in 57 deaths, and caused $60 billion in damages (in 2013 dollars).

Landslides

• The downward movement of rock, earth, or debris, usually under the influence of gravity.
• A large landslide in 2014 at Oso, Washington, killed 43 people and covered a valley with at least 20 feet of debris.
• Both government and insurance companies refused to pay claims for the 2014 landslide.

Sinkholes

• Depressions or holes that form when the surface layer collapses.
• Typically occur where the subsurface layer is made of soluble bedrock (like limestone) that can be dissolved by water.
• A sinkhole opened in Guatemala City in 2010, taking out a café and resulting in at least 20 casualties.

Landslides Induced by Rainfall

• Occur when soil becomes over-saturated and cannot hold together.
• Rainfall can cause landslides by saturating the soil, increasing its weight, and making it prone to slippage.
• Experts warn of the danger of landslides after heavy rains.

Seismic Hazards

• Ground rupture/faulting: Direct displacement of the Earth's surface along a fault.
• Liquefaction: The transformation of solid ground into a fluid-like state due to seismic shaking.
• Strong motion: The shaking of the ground during an earthquake.
• Tsunami: A giant wave caused by a sudden displacement of water, often triggered by an earthquake.

Other Geohazards

• Various landslide types, including:
  • Seismically-triggered landslides
  • Debris flows
  • Mud flows
  • Rock falls
• Mineral hazards:
  • Asbestos
  • Radon
  • Mercury

Earthquakes

• Earthquakes are sudden ground movements caused by energy release along geological faults or tectonic plate boundaries.
• The epicenter, the earthquake's starting point, is directly below the point on the Earth's surface where the shaking is felt.
• The 1994 Northridge earthquake in California had a magnitude of 6.7, resulted in 57 deaths, and caused $60 billion in damages (in 2013 dollars).

Landslides

• Landslides are downward movements of rock, earth, or debris, typically driven by gravity.
• A major landslide in Oso, Washington in 2014 killed 43 people and covered a valley with at least 20 feet of debris.
• Both government and insurance companies denied claims related to the 2014 landslide.

Sinkholes

• Sinkholes are depressions or holes formed when the surface layer collapses.
• They often occur in areas with soluble bedrock, like limestone, that can be dissolved by water.
• A sinkhole in Guatemala City in 2010 swallowed a café, resulting in at least 20 casualties.

Landslides Induced by Rainfall

• Heavy rainfall can oversaturate soil, causing it to lose stability and lead to landslides.
• Landslides can involve various materials, including soil, rock, and debris.
• Experts warn of the danger of landslides following prolonged heavy rain.

Seismic Hazards

• Earthquakes can trigger various seismic hazards, including ground rupture/faulting, liquefaction, strong motion, and tsunamis.

Landslide Types

• Landslides can be triggered by seismic activity and include debris flows, mud flows, and rock falls.

Mineral Hazards

• Certain minerals, such as asbestos, radon, and mercury, pose geological hazards.