GEOS 2104 Test 2

Cinder Cone

much steeper, created by pyroclastic eruption, most are a mix of felsic and mafic

Name the rock type formed by heating and melting rock and then it cooling and forming back into a rock

Igneous Rock

Magma

Molten rock beneath the earth's surface

Where on Earth are igneous rocks created?

Subduction zone, seafloor spreading, hot spot

Subduction zone

The oceanic lithosphere goes down and takes water down with it, when it reaches the asthenosphere, when you add water, you lower melting point and get partial melt

Seafloor spreading

As two plates move apart, asthenosphere moves up, reduces pressure, and lowers melting point so you get partial melt, all ocean crust has the same rock composition

Hot spot

A place deep in the mantle that's very hot so there is a plume of rising things and there is a release of pressure. Plate moves past and a new volcano is formed (e.g. Hawaii, Yellowstone)

Examples of where Hot Spots are?

Hawaii, Yellowstone

Felsic

Minerals that are more rich with silica, Al, Na, Ca and K

Which minerals are felsic?

Mica, feldspar, quartz

What tectonic setting are felsic minerals created?

subduction zone and continental crust

Where in the earth are felsic minerals?

Crust

Intermediate

In between felsic and mafic

Mafic

Minerals that are more rich in Fe, Mg and not very rich in silica

Which minerals are mafic?

Pyroxene, olivine, amphibole

Where in the earth are mafic minerals?

Mantle, some in the core

At what tectonic setting are mafic minerals created?

Spreading centers, hot spots, oceanic crust, and continental crust

Bowen's reaction series

A plot of melting temperature of the minerals, also shows crystallizing order.

What is the sequence of minerals on the Bowen's reaction series chart?

Olivine
Pyroxene
Amphibole
Biotite

Where are ultramafic minerals?

Mantle

When do mafic minerals crystallize out of a melt?

first

When do felsic minerals crystallize out of a melt?

last

When do mafic minerals melt when a rock is heated?

last

When do felsic minerals melt when a heat is heated?

first

Partial melt of an ultramafic rock produces magma of what composition? at what tectonic settings

mafic magma, Spreading centers, hot spots, subduction

Partial melt of an mafic rock produces magma of what composition? at what tectonic settings

Felsic magma at subduction

what is the composition of oceanic crust? what rocks?

mafic, igneous

what is the composition of continental crust? what rocks?

Felsic, Intermediate, Mafic

How can you tell a volcanic (\=extrusive) rock from a plutonic (\=intrusive) rock?

volcanic rocks are extrusive because they form at surface. plutonic rocks are intrusive because they form at depth

Volcanic

formed at the surface

Plutonic

formed under the surface

Volcanic

extrusive

Plutonic

intrusive

What size crystals are in a volcanic rock?

Smaller crystals

What size crystals are in a plutonic rock?

Larger crystals

Describe granite (felsic/mafic)

felsic

Describe granite (volcanic/plutonic)

plutonic

Describe granite (minerals)

quartz, potassium, feldspar

Describe rhyolite (felsic/mafic)

felsic

Describe rhyolite (minerals)

quartz, potassium, feldspar

Describe rhyolite (volcanic/plutonic)

Volcanic

Describe diorite (volcanic/plutonic)

Plutonic

Describe diorite (felsic/mafic)

intermediate

Describe diorite (minerals)

feldspar, amphibole, pyotine

Describe andesite (felsic/mafic)

intermediate

Describe andesite (volcanic/plutonic)

Volcanic

Describe andesite (minerals)

feldspar, amphibole, pyotine

Describe gabbro (felsic/mafic)

mafic

Describe gabbro (minerals)

feldspars, pyroxene

Describe gabbro (volcanic/plutonic)

Plutonic

Describe basalt (felsic/mafic)

mafic

Describe basalt (minerals)

feldspar, pyroxene

Describe basalt (volcanic/plutonic)

Volcanic

Describe peridotite (felsic/mafic)

ultramafic

Describe peridotite (volcanic/plutonic)

Plutonic

Describe peridotite (minerals)

pyroxene, little garnet, olivine

Viscosity

Ability of a material to resist flow

Does felsic magma have higher or lower viscosity?

Higher

Does mafic magma have higher or lower viscosity?

Lower

Lava flow

volcanic eruption, flows fairly easily/fast, mafic

Shield volcano

Produces a lava flow, rather flat, liquid comes out and flow down hill, looks like a curve, mafic rocks that flow easily and come out of cracks

Why does Shield Volcano have its shape?

Shield Volcano has wide shape because lava flows down side

Fissure Eruptions

Lava flow eruption from crack shape rather than typcial pipe shape

Pillow Basalt

underwater lava flow cooled by water to form rocks that are about 1 meter big

Pyroclastic eruption

Felsic, high explosion explosion that that throws stuff in the air, at subduction zones, more silica rich

Cinder Cone

A high steep volcano that is produced by pyroclastic eruptions

Composite Cone

Has a pyroclastic eruptions and lava flows. Most subduction zones are like this, mixed composition: felsic and mafic, what we think of when we think of volcanoes

What type of volcano is formed at mid-ocean ridge(sea-floor spreading)? violent or smooth flowing?

Fissure eruptions, basaltic lava, mafic magma, smooth flowing

What type of volcano is formed at hot spot? violent or smooth flowing?

Shield volcanoes, smooth flowing

What type of volcano is formed at subduction zone? violent or smooth flowing?

Composite cones

Explain role of Viscocity

The more mafic the magma is the more it flows and the more felsic it is the more explosive it is

Explain role of gas bubbles

the speed magma rises affects how fast these escape, if if they escape rapidly(gassy) more likely to explode if they release slow(flat) then it is less likely to explode

Ash

Smaller particles when they become solid

Bomb

Larger things that become solid in air( volcano eruptions)

Pyroclastic flow (nuées ardente)

Gas and ash, heavier than air, so it flow downward, speed of avalance, temperature of magma, goes into valley (what happened in pompeii)

Lahar

Ash + water\=mud, when there is snow on top of the volcanoes, liquid mud flows, speeds of 10's of km per hour

Lava

For the most part slow enough to evacuate, but can have fast flow, varying speeds

Intrusion

the movement of magma from a magma chamber to a different surface location

Volcanic neck

Line of a peak, plumbing system

Dike

Large mound (crack), the tall part that goes up

Pluton

Magma chambers, domes, plutonic rocks

effects of volcanic rocks and ash

rich soil

effects of ash in atmosphere

Climate: global cooling for couple of decades by reflecting sunlight

effects of gas

Created Earth's atmosphere and oceans
Climate: global warming, last 10,000-100,000 years

effects of hydrothermal circulation (hot groundwater):

Hot Groundwater convection near igneous intrusion
Uses: - geothermal energy source
- creates many ore minerals

Permeability

The ability of a rock to let water flow through it

Fractures

cracks, rocks easier/harder to break based on characteristics of these

Unfractured plutonic rocks strength and permeability

Very strong, very low permeability

Volcanic rocks strength and permeability

Weak, permeable

Where on Earth are sedimentary rocks made?

Earth's surface

Weathering

Mechanical and chemical breakdown of rocks

Erosion

Mechanical transport of rock fragments

List mechanical erosion methods

Water, wind, ice, gravity

Clast

tiny pieces that used to be rocks

Describe the amount and clast size that wind can carry

Smallest amount, smaller clasts

Describe the amount and clast size that water can carry

Smallest amount, clasts depending on speed

Describe the amount and clast size that glaciers can carry

Second largest amount, smaller clasts

Describe the amount and clast size that gravity can carry

Largest amount, any size clast

Chemical erosion

Dissolve minerals and rock particles in water

Deposition

Drop the fragments, slows down and stops