Geology and Volcanoes: Key Concepts from Yellowstone to Hawaii

If you were hiking on a Hawaiian volcano and picked up a rock, you would most likely be able to describe it as what?

Basalt

Bridalveil Fall is approximately how tall and is across the valley from what major rock monolith?

~620 feet tall; El Capitan

How could you determine if a basalt layer between sedimentary layers is a lava flow or a sill?

Lava flow bakes only below and has vesicles on top; sill bakes above and below

Why are there so many active volcanoes in the Cascade Mountains?

Subduction of the Juan de Fuca Plate beneath North America

Ash and dust, lapilli or cinders, and blocks and bombs are all types of what?

Tephra (pyroclastic material)

What types of rocks would you likely observe at Mount Rainier National Park?

Andesite, dacite, basalt, volcaniclastic rocks

What feature is responsible for volcanism at Yellowstone National Park?

Mantle hotspot

How do volcanoes at Hawaii differ from those at Mount Rainier and Yellowstone?

Hawaii: basaltic shield volcanoes; Rainier: andesitic stratovolcano; Yellowstone: rhyolitic caldera

When large volumes of magma erupt quickly, the rock above collapses leaving what feature?

Caldera

What type of volcano was Mount Tehama?

Stratovolcano (composite volcano)

What is exfoliation jointing and how does it form?

Sheet-like fractures caused by unloading and pressure release

Which basaltic lava flow has a smooth, ropy surface?

Pāhoehoe

How does water affect the melting temperature of silicates?

It lowers the melting temperature

Which Yellowstone thermal feature precipitates carbonate?

Mammoth Hot Springs

What submarine volcano is forming southeast of the Big Island of Hawaii?

Kamaʻehuakanaloa (Lōʻihi)

What is Wizard Island and when did it form relative to Mount Mazama?

Cinder cone formed after Mount Mazama collapsed

What is the difference between Bumpass Hell and Devil's Backbone?

Bumpass Hell is hydrothermal; Devil's Backbone is a dacite lava spine

What are the Royal Arches and how did they form?

Granite arches formed by exfoliation and erosion

Differences between shield and composite volcanoes are primarily due to what?

Magma composition, viscosity, and gas content

Which minerals crystallize first as magma cools?

Olivine and calcium-rich plagioclase

What is the longest, lowest-terminus, and deepest glacier in the contiguous U.S.?

Emmons Glacier

What is Yellowstone National Park named after?

Yellowstone River ("Yellow Rock River")

Which volcanoes on Hawaii's Big Island are currently active?

Mauna Loa and Kīlauea

What river flows into Crater Lake?

None

How is volcanism at Lassen and Mount Rainier similar and different from Yellowstone?

Lassen/Rainier: subduction; Yellowstone: hotspot

How did the Diorite of North America form and what is the age of granite xenoliths?

Intrusive igneous; granite xenoliths are older

What coarse-grained igneous rock has ~50% silica and is rich in pyroxene?

Gabbro

How can you tell low-grade from high-grade metamorphism?

Index minerals, foliation, crystal size

What volcanic features are common at stratovolcanoes like Mount Rainier?

Lava domes, pyroclastic flows, lahars, steep cones

When did Yellowstone Caldera form?

~640,000 years ago

Which direction is the Pacific Plate moving relative to the Hawaii hotspot?

Northwest

What volcanic rocks are associated with The Pinnacles?

Rhyolitic tuff and breccia

What are Chaos Crags and when did they form?

Rhyodacite lava domes formed ~1,100-1,200 years ago

What rock type dominates Yosemite National Park?

Granite

If an intermediate igneous rock partially melts, what is the melt enriched in?

Silica (felsic components)

What processes cause metamorphism?

Heat, pressure, and fluids

What eruption occurs along a linear vent with little explosive activity?

Fissure eruption

What type of volcano is Mauna Loa?

Shield volcano

What is the relationship between Brokeoff Mountain and Mount Tehama?

Brokeoff Mountain is a remnant of Mount Tehama

How did Nevada Falls form?

Glacial carving followed by river erosion

How do aphanitic igneous rocks form?

Rapid cooling at or near Earth's surface

How does volcanism at Hawaii differ from Yellowstone?

Hawaii: basaltic effusive shields; Yellowstone: rhyolitic explosive caldera

Why are the Painted Dunes red, brown, and yellow?

Iron oxidation and hydrothermal alteration