Earth, Space, And Science Survey Chapter 7 Study Guide

Pumice

Pyroclastic material that is classified by texture and composition. _________ are vesicular rock with an andesitic of felsic composition.

Fumaroles

a vent in a volcanic area (flank) from which fumes or gases escape

Water

All magma contains a small percentage of _______ and other gases. This creates the pressure of a soda being shaken up.

Role of Heat (in partial melting)

On average, temperature increases 20 degrees C to a 30 degree C per kilometer in the upper crust. This change in temperature is known as the geothermal gradient. At high temperatures, rocks in the upper mantle near their melting point and in come locations, partial melting may occur. Another source of energy to melt crustal rocks come from rising basaltic magma.

50+

Over the past 200 years, more than _______ volcanoes have erupted in the united states.

Scoria

Pyroclastic material that is classified by texture and composition. _____ are vascular ejecta with a basaltic composition. Commonly the size range of lapilli.

Partial Melting

incomplete melting of igneous rock that produces the majority of magma. When ___________ _______ occurs, the liquid portion separates from the same material and rises towards the earth's surface due to density differences.

Difference between Sills and buried lava flows.

1.) Upper portions of lava flows usually contain voids produced by entrapped gas bubbles and only the rocks below show evidence of metamorphism. 2.) Fragments of the overlying rock wall will occur in sills and metamorphism exists above and below sills.

Conduit or pipe

As gas rich magma moves up this linear crack, its path typically follows a circular ____________ or _____.

Convergent Plate Boundaries

As oceanic crust beings to subduct, an increase in temperatures and pressures drives of volatiles. These fluids migrate upward to from a wedge-shaped piece of mantle between the subducting and overriding plate. After this rocks begin to melt generating a magma of basaltic composition. Over time, these form Volcanic arcs, and continental volcanic arcs.

Parasitic cones

Eruptions on the sides (flanks) of a volcano that extrude lava that produce small features that are termed _________ ______

Kilauea

Hawaii's _____________ volcano generally erupts quietly with fluid basaltic lava. Occasionally fountains of lave can spray hundreds of feet into the air. Since its latest eruption began in 1983, over 180 homes have been destroyed from the lava flows.

Silica rich magmas

Highly Viscous, __________ ______ _______ may produce explosive clouds of hot ash and transition into plumes termed eruption columns. When this magma ascends, the gas bubbles cannot escape easily and result in the magma expanding which adds more pressure to the volcano. If this pressure exceeds the strength of the overlying rock, fracturing occurs. This creates another scenario that can result in an explosive eruption is the collapse of a volcanoes flank as seen in the St. Hellen's eruption Most explosive eruptions are followed by extrusion of degassed lavas.

Concordant

Igneous plutons are parallel to existing rock structures are termed __________.

Tubular or Massive

Igneous plutons vary in shape and size and are classified as either _____________ or __________ they are also categorized by being discordant and concordant.

Crater

Located at the summit of most volcanoes is a funnel shaped depression termed a _________.

90%

Most Lava on earth _______ has a basaltic composition. Due to the low silica content, hot basaltic lava is relatively fluid. These flows can occur in thin, broad sheets or in a stream-like channel.

Divergent Plate Boundaries

Most magma is produced along the mid-ocean ridge system associated with seafloor spreading. Lithospheric plates are moving apart and the reduction in overlying pressures causes rocks to melt without the addition of heat (decompression melting) Magma is generated of basaltic composition. Most spreading centers are located in the ocean. But some are not.

Discordant

Plutons that can cut across existing rock structures are termed ___________.

Stocks (massive and discordant)

Smaller than Batholiths, intrusive bodies are termed ___________. They are less than 100km2 and may actually be batholiths but have not been fully exposed yet.

Calderas

Some volcanoes have extremely large circular craters that exceed 1km in diameter and these are called __________.

amount of volatiles (gases)

The ___________ __ ___________ also affects mobility. Water dissolved in magma decreases viscosity because it breaks that silicon-oxygen bond. Since the _________ are lost when the molten material reaches Earth's surface, lavas tend to become more viscous.

Destruction of St. Pierre

The ________________ ___ ___ _______ occurred on may 18th, 1902 a nuee ardente formed from the eruption of mount pele on the Caribbean island of Martinique. This completely destroyed the town of St. Pierre and killed almost all of the 28,000 residents one person survived who was a prisoner. Very few people on board ships in the harbor also survived. This destructive event left only a thin layer of volcanic debris on the ground, but the force of this material knocked over brick walls, uprooted trees, and moved cannons.

Yellowstone type calderas

The collapse of a large area resulting from the extensive release of silica rich pumice and ash along ring fractures is called _________________ _______ ________. Example Yellowstone

Crater Lake type calderas

The collapse of the composite cone summit following an explosive eruption of silica-rich pumice and ash is called ____________ _______ _____ _______. Example Crater Lake (oregon)

Hawaiian type calderas

The collapse of the top of shield volcano caused by underground drainage of the magma chamber results in _____________ __________ ____________ Example Mauna Loa (Hawaii)

Water vapor 70%, carbon dioxide 15%, nitrogen 5% and smaller amounts of chlorine, hydrogen and argon.

The composition of gasses in magma is important because they contribute to the gases in our atmosphere. An analysis of the recent eruptions in Hawaii indicate that the gases emitted are ________________________________________________________________________________________________________________________.

Vent

The conduit ends at the surface opening which is termed a _____

Volatiles

The gases (__________) of magma make up to 1 to 6% of the total weight. Although this may seem like an insignificant amount, the quantity of gases can exceed thousands of tons per day.

Pyroclastic material

The gases in magma propel lava to great heights. Particles, produced as gases expand and blow pulverized rock, lava, and glass fragments are called______________ ________

Tamu Massif

The largest known volcano is ________ _______.

Fissures (flood Basalts)

The largest volume of volcanic material is extruded through fractures in the Earth's crust termed _____________. These produce low-viscosity basaltic lava which can cover a large geographic area. The term flood Basalts is commonly used to describe these. The fluidity of this material can allow lava to stay molten long enough to flow 90 miles from its source.

The magma's composition, temperature, and amount of dissolved gases.

The primary factors contributing to weather a volcano erupts gently or violently are:

intraplate activity

This igneous activity is not associated with a plate boundary. This results from excessively hot mantle material 100-150 degrees C which is hotter than normal and is termed mantle plume rising to the suface. This ar4ea in which this basaltic magma erupts is termed a Hot Spot. Over 100 hot spots have been identified and most have been active for millions of years. Example Yellowstone, Canary Islands, and Galapagos islands.

Mount Rainier

This volcano in Washington has year round snow and ice on its peak. Over 100,000 people live in valleys around this volcano. Many homes and businesses are built on lahar deposits from previous eruptions and this is a huge hazard zone.

Along convergent and divergent boundaries, as well as intraplate activity.

Three zones of volcanic activity and plate boundaries. Hint-Igneous activity rarely occurs associated with transform fault boundaries.

Aa flows and Pahoehoe flows

Two types of basaltic lava flows

Shield volcanoes, cinder cones, and composite cones.

Volcanologists recognize three major volcanic types and they are?

Basaltic Magmas

Very Fluid ______ __________ allow for expanding gases to vent with relative ease. As these gases escape, they can produce lava fountains. These eruptions are generally quiescent. Therefore they are relatively quiet.

Role of Volatiles

Water content plays a major factor in determining the temperatures at which a rock will melt. Volatiles (gases) cause rocks to melt at lower temperatures. A fluid rich rock will melt at lower temperatures than a rock without volatiles. Water is an important factor in magma generation along subduction zones. Melting points can be lowered by as much as 100 degrees C with the addition of 0.1 % water

decompression melting

When confining pressure drop enough ________ _______ occurs. This happens when a rock ascends due to convective upwelling moving the rock into zones of lower pressure. ________________ _________ generates magma along divergent boundaries and magma associated with hot spots.

Gases

_________ also propel magma from a volcano. The greater amount of ________ the greater potential for a violent eruption.

Lava Tubes

_____ _____ are openings that are preserved as molten material flows. these allow for lava to flow great distances from its source.

Ring of fire

_______ _____ ______ is located around the Pacific Ocean. Consists of composite cones that erupt volatile-rich andesitic (intermediate) magma. Occasionally erupt violently. Examples Mount St. Helens.

Aa Flows

_______ _____ are surfaces of rough jagged blocks with extremely sharp edges and spiny projections

Cinder Cones (Scoria Cones)

_______ _________ (also called scoria cones) are built from ejected lava fragments. Pyroclastic material size ranges from fine ash to bombs. Most of the material is pea-to-walnut sized (lapilli) that is vascular (has holes) and is black to reddish-brown in color. These types of volcanoes can occasionally extrude lava from the base of the structure. This type of volcano is the most abundant type of the major volcanic types. One of the SMALLEST volcano types and has a steep slop up to 40 degrees. Posses large, deep craters relative to their small size. Most of these volcanoes have a single short-lived eruption. 95% of these volcanoes are produced in less than one year and 1/2 are produced in one month.

High Temperatures

_______ __________ of magma cause it to rise generating cracks. As the gases rise with the magma, they expand creating larger cracks. Some eruptions generate large gas plumes that rise high into the atmosphere.

Dikes (tubular and discordant)

________ are sheet-like (tubular) bodies produced when magma is injected into fractures that cut across rock layers (discordant). Typically form vertically. When exposed by erosion, they typically have the appearance of a wall structure.

Sills (tubular and concordant)

________ are tubular plutons formed when magma is injected along sedimentary bedding surfaces (concordant). Horizontal ______ are most common, however all orientations exist. _____ are formed from very fluid basaltic magma. Injection of a ______ requires that the overlying rock unit be lifted to a height equal to that of the ______.

Nevado del Ruiz

__________ ___ ____ is a Colombian volcano (17,400 foot) that erupted in 1985. Pyroclastic material melted snow and ice which saturated ash and dust. This material flowed down three river valleys on the flanks of the volcano at 60mph. 25,000 people died.

Welded Tuff

__________ ______ occurs when ash falls and fuses together.

Mount St. Helens

_________ __ _________ erupted on Sunday May 18, 1980. This eruption was the largest human recorded volcanic eruption in North America. The blast blew out the entire north flank of the volcano, which lowered the elevation of the volcano by more than 1350 feet. 59 lives were lost, some perished from the intense heat, some from the could of ash and gasses, some from the objects hurled from the blast and some from being trapped in mudflows. Trees were flattened, Lahars flowed 18 miles down the Toutle River. Ash was blown 11 miles in the atmosphere.

Mauna Loa

_________ ____ is a large volcano. It is one of the five overlapping volcanoes that make up the big island of Hawaii. It is 6 miles high with a slope of 10 degrees with a relatively flat summit. Large caldera (1.6 by 2.8 miles and a average depth of 500 feet). The result of eruptions that have occurred over a million years. Lava is extruding from the summit as well as rift zones on the flank of the structure.

Deep Ocean Basin Volcanoes

__________ ________ _______ ____________ erupt a very fluid basaltic lava. These also include submarine volcanoes that dot the ocean floor including those associated with the mid ocean ridge system. Example Hawaii and Iceland

Pahoehoe Flows

__________ _________ have smooth surfaces that resembles twisted braids of rope. Dog wrinkles. This type of lava flow has a higher temperature than aa flows, and can turn into aa flows as they cool or move down slopes. This type of flow typically moves at very slow rates.

Plutons

__________ are geologic structures composed of magma that crystalized inside the earths surface.

Blocks

__________ are particles larger than lapilli made of hardened lava. (64mm or 2.5 inches or larger)

Bombs

__________ are particles that are larger than lapilli made of incandescent lava. May take on a streamlined shape since they are ejected as molten material.

lahars (mudflows)

__________ are volcanic mudflows that develop when volcanic debris (typically ash and dust) become saturated with water and rapidly move downslope. These usually follow stream valleys and gullies. _________ can from when large volumes of snow and ice melt during an eruption, or during heavy rainfall events (these develop when the volcano is not erupting).

Paricutin

___________ is the corn field volcano. It is one of the volcanoes that have been observed from initial eruption to extension. Located 200 miles west of Mexico City. This volcano began erupting on Feb. 20, 1943 In Dionisio Pulido's corn field. Two weeks prior to the eruption numerus earthquakes struck the area. Initial eruption consisted of gas emissions from a depression in the corn field. During the day of the eruption the volcanic structure grew 130 feet in elevation. By the 5th day the cone was 330 feet. Lava flows began from the north side of the volcanic cone. In June 1944 an aa flow 30 feet thick covered much of the town.

Lapili (Pyroclasts)

____________ are pyroclasts the size of small beads to walnuts. (2-64 mm) These are also commonly called Cinders

Laccoliths (massive and concordant)

____________ form in the same manner as sills (concordant) However, these result from more viscous magma resulting in the magma collecting a lens-shaped mass (massive) that arches the overlying strata upward

Kilauea

____________ is located on the island of Hawaii in the shadow of Mauna Loa. This is the world's most active volcano as it has been erupting consistently since 1983. Most activity occurs on the flanks of the volcano in a region called the East Rift Zone. Has erupted more than 50 times since the record keeping began in 1823. Prior to an eruptive phase the volcano inflates towards the surface. Up to 24 hours prior to an eruption, swarms of small earthquakes precede the eruption.

pyroclastic flow (nuee ardente)

_____________ _____ can often develop associated with the explosive eruption of composite cones. These consist of gas infused with hot ash and larger rock fragments that flow down the flanks of volcanoes. Also referred to as Nuee Ardente. Most form from the collapse of a tall eruption column which develops during a violent volcanic eruption.

shield volcano

_____________ ____________ are generated from the accumulation of fluid basaltic lavas. They exhibit a broad, slightly domed structure. Most have grown from the ocean seafloor to form islands, however, some can form on continents. They contain very small amounts of pyroclastic material and their eruption style is quiet. Largest volcano type. Examples are Hawaii, Iceland, and the Galapagos islands.

temperature

______________ has an obvious role in viscosity. When lava cools and begins to solidify, its mobility decreases and eventually the flow of lava stops.

composite cones (stratovolcanoes)

_______________ _________ volcanoes are most located in a narrow zone that surrounds the Pacific Ocean. They are very large symmetrical structures composed of lava and pyroclastic deposits. Mostly produced from gas-rich magma of andesitic composition. They can occasionally extrude material of basaltic and granitic compositions. Magma is thick and does not travel far. May generate explosive eruptions or erupt quietly. They tend to have very complex development histories due to their explosive nature. This type of volcano has two types of building layers as it is composed of lava and pyroclastic materials. Example Mount Mayon. (Philippines), Fuji (Japan) and Vesuvius (Italy)

Ash and dust (pyroclasts)

_______________ ____________ are produced when lava contains so many glass bubbles that it resembles a froth, producing very fine glassy fragments.

Chemical Composition

________________ _______________ is the most important to viscosity than temperature. Magma is directly related to silica content; the more silica, the greater its viscosity. Magmas that produce basaltic rocks contain around 50% silica. Magmas that produce granitic rocks contain over 70% silica. This is due to silicate structures linking in long chains before crystallization begins.

Batholiths (massive and discordant)

________________ are intrusive bodies (massive) with a surface exposure of more than 100km2. These are the largest intrusive igneous bodies (discordant). Typically several hundred kilometers long and up to 100 kilometers wide. Usually composed of granitic rock and may compose the cores of mountain systems and stable interiors of continents (shields)

Irregular distribution on continents

____________________ ___________ ____ ___________ volcanoes that erupt with material which varies from very fluid basaltic lavas, to explosive silica-rich eruptions of granitic magma (rhyolitic) Examples Mount Kilimanjaro.

Role of pressure (in partial melting)

pressures within the earth also increase at depth. Melting (which is also accompanied by an increase in volume) occur at higher temperatures at depth because of greater confining pressures. An increase in confining pressures causes an increase in the rock's melting temperature. Reducing confining pressures lowers a rock's melting temperature.

Volcanic Neck

solid igneous core of a volcano left behind after the softer cone has been eroded