Quarter 2 Quiz 2 Redo Flashcards
Volcano extinction
Volcanoes can be grouped into major categories based on their status
Active: currently erupting
Dormant: not currently erupting, but believed to be potentially active
Extinct: future eruptions not possible (no source of magma underground)
What is a volcano
Volcanoes are features in which magma is transported to the surface via a plumbing system that feeds one or more vent (where volcano erupts from)
Parts of a volcano
LOOK UP PICTURE OF VOLCANO
Conduit will transport magma from the magma chamber to the central vent, where it leaves the volcano, although some magma may end up leaving through one or more side vents
Some magma is stored underground above the magma chamber in horizontal pools known as sills, or vertical ones (usually along rock fractures) called dikes
LOOK AT VOLCANO PIC ON DOC
Magmatic Differentiation
Rocks of varying composition can arise from a uniform parent magma and ice versa
Process is a result of the fact that minerals have different crystallization (melting) temperatures
Once partial melt forms, it can migrate upwards, leaving the solidified minerals behind (precipitate)
Migrating partial melt can pool in magma chamber, and then eventually erupt
As the temperature of the magma changes, it can form different rocks’
Various minerals in the rock have various melting points…….
Thus, from the same igneous rock formations, magma can have very different compositions. Bowen’s Reaction Series:
Magma becomes more felsic as temperatures decrease because silicate minerals are the last to crystalize (they have the lowest melting points).
Bowen’s Reaction Series
Various minerals in the rock have various melting points
From the same igneous rock formations, magma can have very different compositions. Bowen’s Reaction Series
LOOK AT PIC ON DOC
Rock thats melting into magma, magma that’s cooling into a rock
As puddle cools down, some minerals become solid while others stay liquid
Hotter magma forms more mafic rock, low silica minerals crystallize faster and crystallize at a higher temperature
In order to melt mafic stuff into a rock, magma has to be hot
How magma generation happens in nature
Mid-Ocean Ridges
Subduction Zones
Mantle Plumes
How to melt rock
Increase temp
Decrease pressure (reduces melting point)
Add water (which reduces melting point because it acts similarly to how salts do to ice; interferes in bonds, acts as ‘network modifier’)
Do any or all and you can melt rock into magma
Mid-ocean ridges (seafloor spreading)
Decompression melting: hot solid (or mostly solid) rock is pushed up from the mantle
A reduction in pressure decreases the melting point, liquifying hte rock
Mantle upwelling ( as mantle comes up to fill in gap) occurs as a response to tectonic plate divergence; plates pull apart, and the mantle pushes up to fill the gap
Mantle plumes
Not fully understood
May explain volcanoes that form outside of the boundaries of tectonic plates
Molten rock rises to the surface in a specific area, melting by decompression, this area is hotter than its surroundings, likely due to uneven heat distribution inside the Earth
Random pocket of hot in the Earth, as hot rock rises, melts due to decompression (already hot enough to melt, crushing pressure is keeping it solid, when pressure eases, it melts)
Subduction zones
Convergent plate boundaries
Ocean-Ocean or Ocean-Continental
Denser Plate Subducts (usually oceanic or older plate)
One plate subducts under another, water helps melt the rock
Eruptions and magma composition (viscosity)
Eruptions vary depending on the composition of magma
One of the main reasons why is the viscosity, or ‘stickiness’ of magma
Felsic magma is more viscous
Mafic magma is less viscous
Honey is more viscous, water is less viscous
More silica you have, the more viscous, the more ‘sticky’ it will be (more silica in felsic material, less silica in mafic material)
MORE VISCOUS MEANS MORE EXPLOSIVE ERUPTION
types of eruptions general info
Generally volcanic eruptions can be EXPLOSIVE or EFFUSIVE based on the COMPOSITION OF MAGMA
Felsive is most viscous, mafic magma is less viscous
More
Basaltic eruptions
Low silica basaltic magma has low viscosity and can therefore flow relatively easily
Rarely explosive
Lava flows are common
Andesitic eruptions
intermediate -silica andesitic magma has higher viscosity and therefore flow with more difficulty
Often but not always explosive (sometimes effusive)
Pyroclastic material is common
Most fo the plate tectonic boundary volcanoes are andesitic
Rhyolitic eruptions
High-silica rhyolitic magma has very high viscosity and flows with great difficulty
Very explosive
Pyroclastic material
Major volcano types general
Explosion type dictates volcano form
shield volcano, strato volcano, cinder cone
Shield volcano
Shield volcano
strato volcano
Stratovolcano - large, Andesitic and Rhyolitic eruptions, Felsic (extremely explosive)
most pyroclastic material and lava is ejected with great force; some shoots up, falls down, and builds the volcano up into steep shape
Violent explosions can blow off a piece of the volcano, such as Mt. Saint Helens (Washington State)
cinder cone
Cinder Cones - small (usually less than 300 meters tall), usually occur in areas with other volcanic activity, Basaltic to andesitic eruptions (mildly explosive eruptions)
Result of scoria piling up around a single vent
Most common type of volcano
Usually only erupt once
What is a sedimentary rock?
A rock made of sediments
Formed from pieces of pre existing rocks or once living organisms
How sedimentary rocks fit into the rock cycle
A rock made of sediments
Formed from pieces of pre existing rocks or once living organisms
Weathering of other rocks, can be made from either igneous or metamorphic rocks being weathered into sediments
What is sediment
Sediment - pieces of stuff (anything that’s naturally occurring
Mechanical and chemical weathering produces the raw materials for soil and sedimentary rock
3 types of sediment and brief info
Detrital or clastic
Chemical or evaporite
Chemical/Evaporate sediments
Ions in solution, carried by water
When water evaporates, salt or mineral deposit is left
Biologic and organic
Biological/Organic sediments
Organic debris (plant and/or animal matter)
Sedimentary rock may include multiple types of sediment, or one type
production of sediments
Rain, wind, ice temperature changes, movement (glaciers, streams rivers) and animals can all weather existing rocks (AGENTS OF EROSION)
Produce sediments
Physical weathering - solid rock is fragmented by mechanical process
Chemical weatherhing - solid rock is chemically altered and dissolved
Lithification process
Sedimentary rocks are produced through lithification
Loose sediments are transformed into solid rock lithification process
Lithification process
Compaction - reduction in pore space
Cementation by calcite, silica, iron oxide
How sediments are transported
Ice, water, and wind can all transport particles of various sizes to another location
Abrasion and rounding
Sorting – arrangement by size
Sediment is transported in 3 ways
In solution
In suspension
Bedload dragging, rolling or hopping along the bottom
How it is transported depends on size, lighter stuff can be suspended in solution, heavier stuff rolls or hops along the bottom
depositional environments
Sediment is transported from its sources eventually coming to rest in:
Continental - rivers, lakes, swamps
Transitional - beach, lagoon, estuaries
Marine - continental shelf, slope, deep sea
direction of pacific plate
The Pacific Plate moves northwest
Metamorphic “families’
The same amount of heat/pressure will produce different rocks from different parent rocks
Ex. sandstone -> quartzite
Ex. limestone -> marble
The same parent rock can form different metamorphic rocks at different grade
how sedimentary strata are formed
A
Sedimentary rocks form in layers called strata, where you can look into the past, rock layers nearer to the bottom are older
Lithosphere
Crust and uppermost (solid) part of the mantle
basis of layer divisions
A
Crust, mantle, and core are divided based on composition
Lithosphere, asthenosphere, stiffer mantle, inner core, outer core, are divided based on mechanical properties - parts of the mantle are in the lithosphere, asthenosphere, and stiffer mantle
how sedimentary strata are formed
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Sedimentary rocks form in layers called strata, where you can look into the past, rock layers nearer to the bottom are older
types of sedimentary rocks
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Detrital (clastic) sedimentary rocks
Clastic texture, classified by size and shape
Chemical and Biological (organic) sedimentary rocks
Consist of ions and compounds released by chemical weathering and precipitated by chemical reactions or by the metabolism of organisms
Clastic are formed from accumulation and lithification of mechanical weathering debris
Chemical are formed when dissolved materials precipitate from the solution
Organic are formed when plant or animal debris accumulate
why sedimentary rocks are important
A
Clues to past environments
Provide information about sediment transport
Rocks often contain fossils, fossils are helpful in determining ancient environments, connections with biology
Important economically - coal, petroleum and natural gas, sources of iron and aluminum (fossil fuels are trapped in sedimentary rock)
Agents of erosion
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Agents of erosion include - gravity (events like landslides and rockfalls), running water, wind, or moving ice. Running water is the most important agent of erosion
Erosion
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describes many processes which work together to lower the surface of the Earth. In the formation of sedimentary rocks, erosion begins the transportation process of moving the broken down material from their original location.
What metamorphism is/how it fits into the rock cycle
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Change due to heat and/or pressure
Can be changes in
Mineralogy - new minerals such as garnets and mica form
Texture - recrystallization
Chemical composition
No melting - if the rock melts and re-cools (solidifies) then it is igneous
new minerals can be formed by the rearrangement of mineral components or by reactions with surrounded material (like fluids that enter the rock)
Parent rock of a current metamorphic rock
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protolith
agents of metamorphic change
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heat and pressure
Contact metamorphism
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Contact - adjacent to an intrusion (touched magma or lava, new minerals or recrystallization, changed in some significant/noticeable way)
no foliation develops
Occurs in rock immediately adjacent to (touching) igneous intrusives (magma)]
Associated with volcanic areas
Can occur together with regional metamorphism
Regional metamorphism
A
Regional - in mountain belts - much more extensive
Folation (alignment of mineral grains) is developed
Regional metamorphic rocks are more common
Foliation can be wave, get deformed because of stress
Depth of burial influences texture, less to most metamorphized: slate, phyllite, schist, gneiss
As rocks go deeper, they are more foliated (rocks at greater depth are more foliated than rocks above them)
Foliation
A
Happens sometimes with regional metamorphism
Folation (alignment of mineral grains) is developed
Foliation can be wave, get deformed because of stress
As rocks go deeper, they are more foliated (rocks at greater depth are more foliated than rocks above them)
Metamorphic grade
A
Increasing intensity of metamorphism (heat + pressure) creates increased foliation
We say this is “higher grade” metamorphism
The same parent rock can form different metamorphic rocks at different grades
LOOK AT PIC ON DOC
What rock would basaltic lava cool into?
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Whatever the extrusive form of basalt is
Where do volcanoes and earthquakes happen?
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Vast majority of earthquakes and volcanoes occur along plate boundaries, some occur at hot spots/mantle plumes
rock age at mid ocean ridges
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Crust is youngest at the plate boundary, and is older the further away from the plate boundary you are.
Older crust is denser than younger crust
continental-continental convergent boundary
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Continental Crust has a low density and is much more difficult to subduct.
Result is often large mountain chains
three types of boundaries
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convergent, divergent, transform
The theory of plate tectonics
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Earth’s surface is broken into about 15 crustal plates, made of the lithosphere, which have been slowly moving and shifting side about 3.4 billion years ago
Why Wegner’s ideas were rejected
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People didn’ believe him, seemed outlandish, we can see: Continents don’t move!!!!!
No proposed mechanism for plate motion: even if they did move, what could move them
Limited understanding of Earth’s layers. The deepest hole ever dug is 7.6 miles (to this day). Novel ways of understanding earth’s layers were needed (radius of earth = 3,958 mi)
Tectonic plate definition
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Chunks of lithosphere floating on a sticky, plastic, asthenosphere
theory of continental drift
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In 1912, Alfred Wegener proposed that all the continents were once together in one supercontinent called pangea that then drifted apart. This was called the Theory of Continental Drift.
evidence for theory of continental drift general
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fossil, paleoclimatic, geological
problems with continental drift
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Wegener proposed a mechanism for drift: Continents plowed through solid ocean floor, tidal forces drove the motion,
Tidal forces are known to be too weak to move continents, hypothesis was largely rejected due to an inadequate mechanism of continental movement.
