Geology and Hollywood Exam 2

Where do volcanoes primarily form?

Along tectonic plate boundaries, especially subduction zones, at divergent boundaries, and over hotspots.

What is the Ring of Fire?

A horseshoe-shaped zone around the Pacific Ocean with the highest concentration of active volcanoes.

What is the solidus?

The temperature at which a rock starts to partially melt.

What does the liquidus refer to?

The temperature at which a rock is completely molten.

What are the three ways to melt a rock?

Decompression melting, flux melting, and heat transfer melting.

What occurs during decompression melting?

Pressure is reduced, allowing mantle rock to melt.

Where does decompression melting commonly occur?

At mid-ocean ridges, rift zones, and hotspots.

What is flux melting?

Melting that occurs when water or other volatiles lower the melting point of surrounding rock.

Where does flux melting primarily take place?

In subduction zones.

What is heat transfer melting?

Melting that happens when hot magma transfers heat to surrounding rocks.

Where do we find heat transfer melting?

At hotspots under thick continental crust and volcanic arcs.

What are the three types of melt?

Basaltic, andesitic, and rhyolitic.

How does silica content affect viscosity?

Higher silica content results in higher viscosity.

Why does silica change viscosity?

Silica forms strong molecular chains, making magma thicker.

Why is viscosity important in volcanic eruptions?

Low viscosity allows for effusive eruptions; high viscosity can lead to explosive eruptions.

What are shield volcanoes?

Broad, gently sloping volcanoes that produce effusive eruptions.

Give an example of a shield volcano.

Mauna Loa in Hawaii.

What are stratovolcanoes?

Tall, steep-sided volcanoes known for explosive eruptions.

Give an example of a stratovolcano.

Mount St. Helens.

What are cinder cone volcanoes?

Small, steep-sided cones made predominantly of pyroclastic material.

Give an example of a cinder cone volcano.

Parícutin in Mexico.

What distinguishes supervolcanoes?

They can produce massive eruptions with a Volcanic Explosivity Index of 8.

Where is the most well-known supervolcano in the US?

Yellowstone.

What are lava flows?

Slow-moving but destructive volcanic material.

What are pyroclastic flows?

Fast, hot clouds of gas and ash that are deadly.

What are lahars?

Volcanic mudflows triggered by melting ice or heavy rain.

What can ash fall cause?

It can collapse buildings, disrupt air travel, and harm lungs.

What gases are significant in volcanic eruptions?

CO₂ and SO₂.

What can tsunamis be triggered by?

Undersea eruptions or volcanic collapses.

What indicates volcanic activity?

Seismic activity, ground deformation, gas emissions, and temperature changes.

What are some preparation methods for volcanic eruptions?

Evacuation plans, monitoring activity, building barriers, and emergency supplies.

How does temperature affect rock melting?

Rocks have different melting points based on their mineral composition.

How does pressure impact rock state?

High pressure keeps rocks solid; lowering pressure allows melting.

What role do water and volatiles play in rock melting?

They reduce the melting temperature of rocks.

What determines the type of volcanic eruption?

Volcano type, magma composition, and viscosity.

What characterizes calderas?

Large depressions formed by a collapsed volcano.

What is the magma type of a shield volcano?

Basaltic (low silica, low viscosity).

What is the magma type of stratovolcanoes?

Andesitic to rhyolitic (medium to high silica, medium to high viscosity).

What type of volcano has the highest silica content in its magma?

Calderas.

Why do supervolcanoes have significant global impact?

Their catastrophic eruptions can lead to widespread ash fallout and climate effects.

What happens during a volcanic eruption involving high-viscosity magma?

Explosive eruptions due to gas buildup.

What is the role of seismic activity in forecasting eruptions?

Small earthquakes indicate magma movement.

What does ground deformation indicate?

Swelling of the volcano, often a sign of impending eruption.

What does monitoring gas emissions tell us?

Changes in levels of SO₂ and CO₂ can signify volcanic activity.

How does temperature change indicate volcanic activity?

Rising heat near vents can lead to eruptions.

What emergency supplies should people have for a volcanic eruption?

Masks for ash, water, food, and other essentials.

Geotherm

The geothermal gradient is the rate at which temperature increases with depth in the Earth's crust, which can indicate geothermal energy potential or volcanic activity.

EAGLET

Explosions

Ash (danger to airplanes, building collapse,

lahars)

Gas (pyroclastic flows, toxic gases)

Lava (flowing molten rock)

Earthquakes

Tsunami

Pahoehoe(basaltic lava)

A type of basaltic lava that has a smooth, ropy surface and is characterized by its low viscosity, allowing it to flow easily.

Aa (basaltic lava)

A type of basaltic lava characterized by a rough, jagged surface that forms when lava cools quickly.

Modern records

studying active volcanoes and

recording phenomena, correlating with other active

volcanoes

Historical records

Documented volcanic events, their impacts on communities and environments, and observations from past civilizations and studies that aid research on volcanic activity.

Geologic history

Mapping and dating volcanic

rocks and ash deposits

Thermal conditions

refers to the temperature and heat-related factors that influence volcanic activity and magma formation.

where are the Subducting plates

Subducting plates are typically found at convergent plate boundaries, where one tectonic plate is forced under another, often leading to volcanic activity.

dome volcano

A type of volcano characterized by a steep, dome-shaped profile formed by the slow extrusion of viscous lava that is typically andesitic to rhyolitic in composition.

magnetic conditions

related to the Earth's magnetic field and its influence on geological processes.

hydrologic conditions

Refers to the various factors affecting water movement and distribution in geological environments, including groundwater flow, surface water interactions, and precipitation patterns.

USGS

The United States Geological Survey, a scientific agency of the U.S. government that studies natural resources, natural hazards, and the landscape of the U.S.

magma characteristics

Its composition can vary from basaltic (low silica, low viscosity) to andesitic (medium silica, medium viscosity) and rhyolitic (high silica, high viscosity). The temperature of magma typically ranges from 700 to 1300 degrees Celsius. Viscosity is influenced by silica content, with higher silica leading to thicker, more viscous magma. The gas content, including water vapor and carbon dioxide, affects the pressure within the magma chamber and can influence the explosiveness of a volcanic eruption.