Geological Catastrophes Flashcards Midterm

What is a catastrophe?

A destructive event that causes major disruption, damage, or loss of life.

What is the difference between a catastrophe and a hazard?

A hazard is a potentially damaging process or event; it becomes a catastrophe when it causes severe harm.

What is the frequency-magnitude relation?

Small events happen more often than large ones; the Gutenberg-Richter law relates earthquake magnitude to frequency.

Why do wealthier nations often have greater economic losses from disasters?

They have more valuable infrastructure exposed to hazards.

What factors can lead to higher death tolls in poorer nations during disasters?

Greater vulnerability, weaker buildings, and less capacity to prepare and respond.

What has caused the reported increase in disasters over the past 50 years?

Population growth, development in hazard-prone areas, and improved reporting.

What is scientific notation?

A way to write numbers as a value from 1 to less than 10 multiplied by a power of ten.

What are the main internal sources of Earth's energy?

Primordial heat from Earth's formation and radiogenic heat from radioactive decay.

What is the difference between energy and temperature?

Energy is the capacity to do work; temperature measures the average kinetic energy of particles.

What are the three methods of heat transfer?

Conduction, convection, and radiation.

How old is Earth?

About 4.54 billion years.

What are the layers of Earth by composition?

Crust, mantle, and core.

What is the lithosphere?

The rigid, brittle outer shell made of the crust and uppermost mantle.

What is the asthenosphere?

A weaker, ductile part of the upper mantle beneath the lithosphere.

What are the three types of plate boundaries?

Divergent, convergent, and transform.

What happens at convergent boundaries?

Two continental plates colliding can build mountains; oceanic plates can sink beneath continental plates.

What is the lifecycle of oceanic lithosphere?

New oceanic lithosphere forms at mid-ocean ridges and is recycled at subduction zones.

What evidence supports the theory of continental drift?

Matching shapes of continents, fossils, rock belts, and evidence of past climates.

What is an earthquake?

Sudden ground shaking caused by rapid release of stored elastic strain.

What is a fault?

A fracture or zone of fractures where rocks have moved.

What is the focus of an earthquake?

The point underground where rupture begins.

What is the difference between a fault and a plate boundary?

A fault is a specific fracture within the crust; a plate boundary is a broad region where tectonic plates meet.

What are the three main types of stress in geology?

Compression, tension, and shear.

What is a normal dip-slip fault?

A fault where the hanging wall moves down, commonly caused by extension.

What is a reverse dip-slip fault?

A fault where the hanging wall moves up, caused by compression.

What are left-lateral and right-lateral strike-slip faults?

Left-lateral means the opposite side moves to the left; right-lateral means it moves to the right.

Can earthquakes be predicted?

Scientists cannot reliably predict the exact time, place, and magnitude of an earthquake.

What are body waves?

P waves and S waves that travel through Earth.

What are surface waves?

Love and Rayleigh waves that travel along Earth's surface.

How is the distance to an earthquake determined?

By measuring the time gap between the P-wave and S-wave arrivals.

How many stations are needed to locate an epicenter?

At least three stations.

What is the Local Richter magnitude?

An early magnitude scale based on the amplitude of seismic waves recorded by a seismograph, adjusted for distance.

What is seismic moment?

Seismic moment measures the physical size of the rupture using fault area, slip, and rock rigidity.

What is moment magnitude?

Moment magnitude is calculated from seismic moment and is the preferred magnitude scale for large earthquakes.

What does Modified Mercalli Intensity (MMI) measure?

It measures the observed shaking and effects at a particular place, including what people feel and the damage observed.

What was the largest recorded earthquake?

The 1960 Valdivia earthquake in Chile, magnitude M_w 9.5, on May 22, 1960.

What are major hazards and effects of earthquakes?

Permanent ground displacement, shaking, and triggered hazards such as landslides, liquefaction, fires, and tsunamis.

How can soft sediments affect earthquake shaking?

Soft sediments can increase the strength or duration of shaking compared with nearby firm rock.

What is resonance in the context of earthquakes?

Shaking becomes stronger when the ground-motion frequency matches a structure's natural frequency.

What is liquefaction?

Water-saturated, loose sediment loses strength during shaking and behaves more like a liquid.

What earthquake is a classic example of liquefaction?

The 1964 Niigata earthquake in Japan.

How do larger earthquakes affect landslides?

Larger earthquakes generally trigger more and larger landslides, depending on slope steepness, geology, weather, and distance from the rupture.

What is the Los Angeles Basin's vulnerability during earthquakes?

Thick, soft basin sediments can amplify shaking; water-saturated loose deposits can liquefy.

How can landslides affect flooding in mountains?

Landslides can dump sediment into river channels, which can block or constrict channels, leading to flooding.

What was a significant hazard of the 2011 Tohoku earthquake?

The devastating tsunami caused widespread coastal inundation and contributed to the Fukushima nuclear accident.

What caused major damage in the 1906 San Francisco earthquake?

Shaking caused major damage, but fires after the earthquake destroyed much of the city.

Where do the largest earthquakes occur?

Subduction zones, where one plate descends beneath another.

Which US regions have potential for large earthquakes?

Alaska, the Pacific Northwest, and California.

What is the San Andreas Fault's expected earthquake magnitude?

The San Andreas Fault is not expected to produce a M>9 earthquake.

What is Japan's seismic activity attributed to?

Japan is highly seismic because it lies where several tectonic plates interact, including major subduction zones.

What is the ongoing geological process in China, India, and Nepal?

The collision of the Indian Plate with the Eurasian Plate builds the Himalaya and creates major earthquake hazards.

What are two ways to forecast earthquake likelihood?

Return-period estimates and seismic-gap hypothesis.

What is earthquake early warning?

Detection of P waves can give people and systems a few seconds of warning before more damaging waves arrive.

Where do most volcanoes occur?

Most occur at divergent boundaries and convergent subduction zones.

What is the difference between magma and lava?

Magma is molten rock beneath Earth's surface; lava is magma that erupts onto the surface.

What are the three Vs in volcanology?

Viscosity, volatiles, and volume.

How does viscosity affect magma?

More silica means higher viscosity because silica-rich melt has a more interconnected structure.

What are common magma volatiles?

Water vapor, carbon dioxide, and sulfur gases.

What is decompression melting?

Pressure falls as hot mantle rises, commonly occurring at divergent boundaries.

What is the Volcanic Explosivity Index (VEI)?

It ranks explosive eruptions using factors such as erupted material volume, plume height, and observations.

What are shield volcanoes?

Broad, gently sloping volcanoes, e.g., Mauna Loa, Hawaii.

What are stratovolcanoes?

Steep-sided layers of lava and ash, e.g., Mount Rainier, Mount Fuji.

What are calderas?

Large collapse depressions formed after major magma withdrawal, e.g., Yellowstone.