GEOL 200 - Midterm 1 - Volcanoes

Natural Hazard (Lecture 1)

A natural event that could cause harm.

Natural Catastrophe (Lecture 1)

A large-scale disaster with long-term effects.

Natural Disaster (Lecture 1)

When a hazard causes damage or deaths.

Risk (Lecture 1)

the chance it will actually cause harm

Hazard (Lecture 1)

Potential threat

Risk vs. Hazard (Lecture 1)

A hazard is the potential threat; risk is the chance it will actually cause harm.

Vulnerability (Lecture 1)

how easily people or places can be harmed by a hazard

Hazard, Risk and Vulnerability Equation (Lecture 1)

Risk = Hazard × Vulnerability.

How is vulnerability assessed? (Lecture 1)

Look at how exposed people are, how sensitive the area is, and how well it can recover.

What factors influenced the number of fatalities following the 2011 Japan earthquake and

tsunami (Lecture 1)

Strong building codes and early warning systems in Japan reduced deaths.

What factors influenced the number of fatalities following 2004 Indian Ocean earthquake and tsunami? (Lecture 1)

little warning, weaker infrastructure, and less public awareness, leading to far more fatalities.

What is a hazard map? (Lecture 2)

Shows where past hazards occurred and where future ones are most likely.

What is involved in hazard assessment? [For both earthquakes and volcanoes] (Lecture 2)

Identify hazards, map past events, measure size + frequency, estimate impact.

What additional tasks have to be carried out for risk assessment? (building from hazard assassment) (Lecture 2)

Exposure — who and what is in the hazard zone.

Vulnerability — how easily those people or structures can be harmed.

Expected losses — estimating potential damage and impacts.

Event recurrence time (Lecture 2)

Average time between events = total time / number of events.

Conditional probabilities and how are they calculated? (Lecture 2)

Conditional probability is the chance that one event happens given that another event has already occurred.

Where (geographically) do we expect largest economic losses from natural disasters? Largest losses of human life? (Lecture 3)

Biggest economic losses: Rich countries with expensive infrastructure.

Biggest human losses: Poorer countries with dense populations and less warning.

Are the costs of natural disasters increasing or decreasing through time? Why? (Lecture 3)

Rising because of population growth and urbanization in hazard zones.

Benefits of living near volcanoes (Lecture 3)

Fertile soil, minerals, geothermal energy, tourism.

How do volcanoes affect soils and local climate? (Lecture 3)

Ash adds nutrients; large eruptions can cool the planet short-term.

Where do diamonds come from? (Lecture 3)

Form deep in the mantle under high pressure and are brought up by kimberlite eruptions.

What are the two most abundant elements in the: 1. Universe? 2. Earth? 3. Crust? (Lecture 4)

Universe - hydrogen and helium; Earth - iron and oxygen; Crust - oxygen and silicon.

What are meteorites? (Lecture 4)

Rocks from space that show what early Earth was made of.

What are the main layers in the Earth? What are their approximate thicknesses? (Lecture 4)

Crust (~5-70 km), Mantle (~2900 km), Core (~3500 km radius).

What are the two types of crust? What are their characteristics? (Lecture 4)

Oceanic = thin, dense, basaltic; Continental = thick, light, granitic

What is a mineral? (Lecture 4)

a naturally occurring, inorganic solid with a specific chemical composition and a definite crystalline structure

What is a rock? (Lecture 4)

one or more minerals together.

What is a biomineral? (Lecture 4)

A mineral made by living things (like shell calcite).

What is the rock cycle? (Lecture 4)

Describes how rocks form, melt, erode, and change type over time. erosion and weathering, sediment burial, seafloor spreading, volcanism, tectonism, sediment transportation and cementation

How do we classify rocks? (Lecture 4)

Igneous (from magma), sedimentary (from deposits), metamorphic (from heat and pressure).

What are three ways we can explore the subsurface of the earth? (Lecture 5)

Seismic waves - studying how earthquake waves travel to learn about its layers.

Drilling - directly collecting rock samples from deep boreholes.

Mantle rocks - studying ophiolites (uplifted ocean crust) and mantle xenoliths carried up by magma.

How deep is the Kola Superdeep Borehole? (Lecture 5)

About 12 km deep - the deepest ever drilled.

What is an ophiolite? (Lecture 5)

a geological formation that is a remnant of Earth's oceanic crust and upper mantle, uplifted and exposed on land

What is a mantle xenolith? A kimberlite? (Lecture 5)

a piece of the Earth's upper mantle rock that was incorporated into volcanic magma and brought to the surface

Experimental petrology? (Lecture 5)

Recreates mantle conditions to study how rocks me

What are P waves? (Lecture 5)

Move through solids and liquids - fastest seismic waves

What are S waves? (Lecture 5)

Move only through solids - cannot travel through liquids.

What is a seismic shadow zone? (Lecture 5)

area on Earth's surface where seismic waves from an earthquake cannot be detected by seismographs

What does the S-wave shadow tell us about the Earth? (Lecture 5)

provides further evidence that earth has a liquid core

What is the boundary between the crust and the mantle called? (Lecture 5)

Called the Moho (Mohorovičić Discontinuity).

How does the Earth's interior cool itself? (Lecture 6)

mantle convection, conduction, and volcanic activity, which transfer heat from deep inside to the surface.

What is the relationship between temperature of rock and the speed at which seismic waves travel through it? (Lecture 6)

Hot rocks slow seismic waves, and cold rocks make them move faster

What are downwellings in the mantle? (Lecture 6)

areas where cold, dense mantle sinks deeper into the Earth, usually at subduction zones

Why do downwellings form? (Lecture 6)

cooler mantle is denser, so it sinks as part of the Earth's convection process

What are upwellings in the mantle? What are they associated with? (Lecture 6)

areas where hot mantle rises toward the surface

associated with mid-ocean ridges and mantle plumes

What is a tectonic plate? [a.k.a. lithospheric plate] (Lecture 6)

a big, solid piece of Earth's outer layer that slowly moves over the softer rock below it

What are the three types of plate boundaries? (Lecture 6)

Divergent - move apart.

Convergent - move toward each other.

Transform - slide past each other.

Divergent Boundary

Plates move apart.

Forms mid-ocean ridges, rift valleys, and new ocean crust.

convergant boundary

Plates move toward each other.

Creates trenches, volcanic arcs, and mountain ranges.

Transform Boundary

Plates slide past each other.

Produces fault lines and earthquakes, like the San Andreas Fault.

What is the relationship between plate tectonics and earthquakes and volcanoes? (Lecture 6)

Most happen along plate boundaries, causing movement and magma activity.

What happens to each of the tectonic plates in a subduction zone? (Lecture 6)

the denser oceanic plate sinks beneath the lighter continental plate, where it melts and can create volcanoes and earthquakes.

What is the subduction zone? (Lecture 6)

where one tectonic plate sinks beneath another

Which plate boundary type are subduction zones associated with? (Lecture 6)

associated with convergent plate boundaries

How does plate age vary on the surface of the Earth? (Lecture 6)

youngest at mid-ocean ridges and gets older farther away from the ridges as it moves outward.

What is melting? (What is different about water from most other substances?) (Lecture 7)

when a solid turns into a liquid as temperature rises or pressure drops

Water is different because it melts at lower temperatures when pressure increases

How does temperature and pressure affect whether a material is solid or liquid? (Lecture 7)

higher temperatures, materials are more likely to be liquid, and at higher pressures, they are more likely to stay solid

What is the solidus? (Lecture 7)

the temperature at which a solid begins to melt and become a liquid

What is the liquidus? (Lecture 7)

the temperature at which a mixture becomes completely liquid

What is the geotherm? (Lecture 7)

the line showing how temperature increases with depth inside the Earth

What are three ways to melt the mantle? (Lecture 7)

1. Add heat.

2. Lower pressure (decompression melting).

3. Add water or other volatiles (flux melting).

Why does the mantle melt above mantle plumes? (Lecture 7)

hot material rises and pressure drops, causing decompression melting.

Why does the mantle melt at subduction zones? (Lecture 7)

because volatiles from the sinking plate lower the melting point of the overlying mantle

Why does the mantle melt at mid-ocean ridges? (Lecture 7)

because pressure decreases as plates move apart, causing decompression melting

How are volcanoes distributed on the Earth? (Lecture 7)

found along plate boundaries at subduction zones, mid-ocean ridges, and hotspots in the middle of plates

How are eruptions classified? (Lecture 7)

plinian, pelean, vulcanian, strombolian, Hawaiian, Icelandic

Plinian Eruption (Lecture 7)

explosive eruption of felsic magma that sends ash and pumice high into the air. It causes pyroclastic flows and heavy ashfall.

EXAMPLE: Mount Vesuvius

Vulcanian Eruption (Lecture 7)

short, explosive burst of viscus magma that ejects ash, gas, and volcanic bombs. It forms dark eruption clouds and can cause pyroclastic flows

EXAMPLE: Sakurajima

Strombolian Eruption (Lecture 7)

basaltic magma with low viscosity. It produces frequent, mild explosions that throw lava bombs and ash into the air

EXAMPLE: Stromboli

Hawaiian Eruption (Lecture 7)

basaltic magma with very low viscosity. It produces gentle lava flows and fire fountains rather than explosions

EXAMPLE: Mauna Loa

Icelandic Eruption (Lecture 7)

basaltic magma with very low viscosity. It creates long lava flows from fissures and little to no explosion

EXAMPLE: Laki

What is a'a? (Lecture 7)

basaltic lava with low viscosity that hardens into a rough, jagged surface

What is pahoehoe? (Lecture 7)

basaltic lava with low viscosity that cools slowly, forming a smooth, rope-like surface.

What are hazards of gas-poor eruptions, like those on Hawai'i? (Lecture 7)

mainly produce lava flows that move slowly but can destroy homes, roads, and land, though they rarely kill people