Chapter 5 Volcanoes and Other Igneous Activity

What is a caldera and when do they form? Also, what are they typified? (pg 3)

A caldera is a gigantic volcanic depression. They form when a magma chamber empties and the volcano collapses into the evacuated space. Also, they are typified by steep sidewalks and flat floors.

What is the difference between a caldera and a crater ? (pg 3)

A caldera is much larger than a crater (one to tens of kms across)

What is a crater and what are they formed as? Also, where are the summit eruptions located and where does the flank eruptions exit? (pg 3)

A crater is a bowl-shaped depression atop a volcano They form as erupted lava piles up around the vent. Summit eruptions are located within the summit crater. Flank eruptions exit the side of a volcano.

List the Volcanic Architectures and the distinctive profiles (pg 3)

A magma chambers, Fissures and vents, Craters and Calderas. The Distinctive profiles are Shield volcanoes, Cinder cones and Stratovolcanoes

A pyroclastic flow is an avalanche of _____________ The eruption cloud ______________ uoyed by a pillow of superheated air, pyroclastic flows can ____________. (at what speed?) (pg 3)

A pyroclastic flow is an avalanche of hot ash, gas, and debris that develops from some silica-rich volcanic eruptions. The eruption cloud collapses and races down the slope of the volcano. Buoyed by a pillow of superheated air, pyroclastic flows can move at speeds of 300 km per hour (186 mph).

What is a volcanic debris flow? When do they occur and how does the flow move?

A volcanic debris flow is wetted debris that moves downhill. These occur where volcanoes are covered with ice and snow or are drenched in abundant rain. Volcanic debris flows move like wet concrete.

What is a Volcano? (pg 1)

A volcano is a mountain constructed by the eruption of molten rock from Earth's interior. Volcanoes are a direct consequence of plate tectonics and mantle convection.

Identify the action of an air-fall tuff (pg 5)

An air-fall tuff accumulates like snow.

Andesite lavas are ? (pg 1)

Andesite lavas are in between low and high viscosity

Describe Rhyolitic eruptions (pg 3)

Andesitic or rhyolitic magmas are more viscous and contain more volcanic gases, which make them more prone to explode. Explosive eruptions generate huge volumes of debris, especially volcanic ash.

As a basalt flow is moving,_____________The hot basalt continues ______________Over time, the crust thickens and flow is_____________Lava tubes are often miles long. Tubes prevent______________After volcanic episodes_________. (pg 2)

As a basalt flow is moving, the upper surface begins to cool and skins over with a crust. The hot basalt keeps flowing beneath the crust. Over time, the crust thickens and flow is entirely contained within the tube. Lava tubes are often miles long. Tubes prevent cooling, facilitating flow for miles. After volcanic episodes, lava tubes become caves that can transmit water, and tourists.

volcanic mud flows (lahars) (pg 2)

Ash and rocks mixed with water. Flows like cement.

(Volcanic Ash and Lapilli) Ashfalls can completely bury what 3 things? Also, Tephra is heavy because? (pg 4)

Ashfalls can completely bury landscapes, killing plants and crops. Tephra is heavy because it causes roof to collapse. Tephra is gritty; it abrades car and airplane engines. Floodwaters easily move tephra as deadly lahars.

Describe the Shape and Composition of a shield volcano? (pg 3)

Broad, slightly domed-shaped, may cover large areas and produced mostly by eruptions of large volumes of basaltic lava

What trigger landslides? Describe what happens during eruptions. (pg 5)

Eruptions can trigger landslides. During eruptions, large masses of material are deposited rapidly near a vent. (These unstable slopes are prone to movement)

Composition (pg 1)

Felsic- Intermediate: more vicious and explosive and Mafic: less vicious and less explosive of a volcanic eruption

(Volcanic Gases) Gas bubbles in magma may be trapped in ______ which are called?

Gas bubbles in magma may be trapped in the cooled volcanic rock which are called vesicles.

How are fragmented lava formed? (pg 5-6)

Hot lava skins over while the interior still flows and the external crust cracks and breaks apart into fragments. Lava quenched in water shatters to form hyaloclastite.

Temperature (pg 1)

Hotter: less vicious and less explosive of a volcanic eruption

What are Lahars and describe the material? (pg 5)

Lahars are mudflows that result when water moves ash. This material is very much like wet concrete, very thick and dense. (It can carry away everything people, houses, bridges).

Lava can be thin and runny or thick and sticky depending on _____________, which is due to _________ (especially silica content), ________ and _____________________ (pg 1)

Lava can be thin and runny or thick and sticky depending on viscosity, which is due to composition, temperature, and gas content

What are Lava Tubes? (pg 2)

Lava tubes are conduits for basaltic lava

What are volcanic explosions caused by? (pg 1)

Magma

Dissolved gases (pg 1)

More dissolved gases: Greater chance of being more explosive, depending on viscosity of magma of a volcanic eruption

Describe the Shape and Composition of a stratovolcano (composite cone) (pg 4)

Most are located adjacent to the Pacific Ocean, large, classic shaped volcano, composed of interbedded lava flows and pyroclastic flows and oftem exhibit very violent volcanic eruptions

Crater (pg 3)

Opening at the summit of a volcano. Very large craters are called calderas

(Volcanic Gases) Gases are expelled as

P drops with magma rise

Rhyolitic Lava Flows have the highest _______ and the most ______ _______. Describe more. (pg 2)

Rhyolitic Lava flows have the highest Si02 and is the most viscous lava. Rhyoltic lava rarely flows. Rather, lava plugs the vent as a lava dome. Sometimes, lava domes are blown to smithereens during eruption.

Give an example of landslides effectiveness.(pg 5)

The eruption of Mt. St. Helens

What makes andesitic lavas viscous(higher viscosity)? describe their flow or more. (pg 2)

The higher SIO2 content makes them viscous. Unlike basalt, they do not flow rapidly. Instead, andesitic flows mound around the vent and flow slowly. The cooled external crust fractures into rubble, called blocky lava.

What are shield volcanoes? (pg 3)

They are broad and slightly dome-shaped (like an inverted shield). They are constructed by a lateral flow of low-viscosity basaltic lava, have a low slope, and cover large geographic areas.

Lava Domes are ? What are they typically formed from? (pg 4)

They are bulbous mass of viscous congealed lava. They are Typically form from felsic or intermediate magma after gas escapes from violent eruptions.

How hot and destructive pyroclastic flows can be? (pg 4)

They are so hot (500oC to 1000oC) that they kill every living thing. They flatten buildings and forests, leaving complete destruction behind.

What does explosive eruptions possess? (pg 2)

They have high gas pressures (from more viscous, SiO2-rich magma) that are released

Supervolcanoes and Caldera Events have what kind of volcanic eruptions? What do they produce? (two) Also, what do they eject when referring to volcanic dusts? (pg 4)

They have the argest volcanic eruptions on Earth. They Produce large calderas as magma chamber collapses after the main eruptive event and extensive welded ash-flow tuffs and ash falls that cover large areas. Also, they eject massive quantities of volcanic dust into stratosphere, blocking the sun and cooling the earth.

How are pyroclastic flow an extremely deadly hazard when considering their speed? (pg 4)

They move 100 to 300 km per hour (62 to 186 mph) on a superheated carpet of air (like on an air hockey table).

What is the important movement basalt flows display? (pg 2)

They move rapidly (up to 30 km per hour) and can flow for long distances (up to several hundred km). Long flow distance is assisted by lava tubes, which form conduits that dramatically slow cooling.

What does effusive eruptions produce? (pg 1)

They produce a vast outpouring of basaltic lava that pours away from vents in rivers of lava. Lava lakes can form near, or inside, the vent. These eruptions can produce huge lava fountains 500 m high.

volcanic eruptions can create giant waves called (pg 5)

Tsunamis

What are the general parts of the different features of a volcano? (pg 3)

Vent, cone and crater.

How and why are volcanic blasts a rare hazard? (pg 5)

Volcanic blast is a rare hazard because most eruptions are vertical. When explosions are ejected sideways, they can create severe blast hazards.

Describe Convective cloud and material (pg 5)

Volcanoes erupt large quantities of fragments—volcaniclastic deposits. This material includes pyroclastic debris, preexisting rock, landslide debris, and lahars.

Pillow basalts are (common feature of the mid-ocean ridge) (pg 2)

are blobs of basalt cooled rapidly by quenching in water. Lava pressure ruptures a pillow to form the next blob. The process repeats to form a mound of pillow basalts

What are stratovolcanoes? (also known as composite volcanoes) (pg 4)

are large, cone-shaped volcanoes with steep slopes made of alternating layers of felsic lava, tephra, and debris. Often symmetric, they can be odd shapes from landslides, etc.

Basaltic (mafic) lava flows are very ? Basalt flows are often ? (pg 2)

are very hot, low silica, and low viscosity. Also, they are often thin and fluid, which facilitates long flow distances.

Describe the Shape and Composition of a cinder cone? (pg 4)

built from ejected lava fragments, steep slope angle and small size

Factors that determine explosiveness of a volcanic eruption (pg 1)

composition, temperature and dissolved gases

(Statues of Volcanoes) Active: (pg 1)

currently erupting or has erupted relatively recently (<10,000 yrs ago).

Tephra is the term to describe (pg 5)

deposits of pyroclastic debris of any size.

Characteristic of a magma determines? (pg 1)

determines the "violence" or explosiveness of a volcanic eruption

(Volcanic Gases) The style of gas escape controls (pg 6)

eruption violence

Volcanic gases (pg 1)

expelled vapor and aerosols

Pyroclastic flows and falls possess ash, cinders, blocks and bombs that does what? (pg 2)

falls from the sky and accumulate in tuffs, or rapidly flow with hot gases downhill to form welded tuffs (Volcanic dust that remains in the stratosphere for years)

Pyroclastic debris (pg 1)

fragments blown out of a volcano

(Volcanic Gases) For high-viscosity rhyolite, gas escape is (pg 6)

gas escape is difficult, resulting in violent release.

(Volcanic Gases) For low-viscosity basalt, gas escape is (pg 6)

gas escape is easy, leading to more mellow eruptions

(Statues of Volcanoes) Extinct: (pg 1)

has not erupted for a very long time and is considered unlikely to do so in the future.

Aa Lava is a ________ word describing __________ that solidifies with a _______, ______, __________ texture. A'a forms when _________________. With flow, the lava crumbles into _______, _________ and _______ that solidify into hard solid rock (pg 2)

is a Hawaiian word describing basalt that solidifies with a jagged, sharp, angular texture. A'a' forms when hot flowing basalt cools and thickens. With flow, the lava crumbles into sharp, jagged shards and fragments that solidify into hard solid rock. A'a' is purportedly what people say when walking on this material barefoot.

Pahoehoe lava is a __________ word describing ______. Pahoehoe forms ___________ when _________ With flow, the skin is rolled into __________ ______ and _________. (pg 2)

is a Hawaiian word describing basalt with a glassy, ropy texture. Pahoehoe forms when extremely hot basalt forms a skin. With flow, the skin is rolled into ropy ridges and furrows.

What is an effusive eruption? (pg 1)

is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground

Tip: Crater Lake, Oregon, is actually ? (pg 3)

is actually a caldera and not a crater

When thinking of volcanoes, land forms are created when (pg 1)

landforms are created when lava and hot particles escape from the Earth's interior then cool and solidify around the vents.

Tuff is considered as (pg 5)

lithified ash, which may or may not contain lapilli.

Describe pyroclastic (pg 5)

material accumulated from clouds of debris that hasn't moved since deposition

Describe fragmented lava (pg 5)

material from broken lava flows

Describe vocalni-sedimentary (pg 5)

material moved after deposition

lava flow (pg 1)

molten rock that moves over the ground

(Statues of Volcanoes) Dormant: (pg 1)

not erupted recently but is considered likely to do so in the future.

Cone (pg 3)

positive landform caused by accumulation of volcanic material around a vent.

Explosive eruptions creates and mostly composed of what compositions? (pg 2)

pyroclastic flows and cover the landscape with tephra. They are mostly andesitic and rhyolitic compositions

Other volcaniclastic deposits consist of any fragmental igneous material. List the three categories: (pg 5)

pyroclastic, volcani-sedimentary and fragmented lava

Many volcanic gases are poisonous (H2S, SO2, CO, CO2) and cause (pg 5)

respiratory illness

Basaltic lavas are _____ with how much viscosity (pg 1)

runny with low viscosity

Vent (pg 3)

surface opening connected to the magma chamber.

What are cinder cones? (pg 4 )

the smallest type of volcano, are cone-shaped piles of ejected lapilli-sized fragments that have built up at the angle of repose around the vent. They are often symmetrical with a deep summit crater.

Rhyolite lavas are ____ with how much viscosity (pg 1)

thick with high viscosity

Explosiveness if different composition magma (product of volcanic eruption) (pg 1)

volcanic gases, pyroclastic debris and lava flows