GEOG 1402- Test 2

Plastiglomerate

a rock composed of a mass of sand, pebbles, small rocks and lock tightly together by melted plastic

* caused by forest fires, lava flows, campfires and on beaches where plastic is burned
* classified as sedimentary

Composition of rocks

a rock is composed of one or more minerals

Rock families

all rocks can be grouped into igneous, sedimentary, and metamorphic rock families

The rock cycle

Rocks are formed, transformed, and recycled into mantle through the rock cycle

Recycling of rocks

Igneous→ sedimentary→ metamorphic→ igneous→

Melting

Mantle material melts into magma by means of decompression melting and flux

Tectonic settings

Igneous rocks form in hot spots, mid-ocean ridges, rift valleys and subduction

Intrusive igneous rocks

cools slowly, allowing time for growth of crystals

Extrusive igneous rock

cools quickly, have smaller or no crystals

Sedimentary rock coverage

covers 75% of the crust’s surface, make up only 4% of the crust

Sedimentary rock types

clastic, organic and chemical sedimentary rocks

Coal

widely used energy source, its mining causes environmental problems

* form from ancient deposits of peat; a brownish back, heavy soil found in wetlands made up of the partially decomposed remains of plants, it is compacted and lithified into it
* sometimes referred to as buried sunshine, b/c it is solar energy stored in plants that grew long ago

Petroleum

* formed from the remains of ancient marine zooplankton and phytoplankton
* is a hydrocarbon, it is a liquid composed of chains or rings of molecules made of hydrogen and carbon

Evaporites

an economically important type of chemical sedimentary rock

* used in lithium ion batteries to construction material
* is a deposit of one or more minerals resulting from repeated evaporation of water from a basin

Sedimentary rocks and earth history

fossils in sedimentary rock reveal ancient life and ancient environments on Earth

Metamorphism

rock of any type can experience, if it is heated, subjected to high pressures, or both

* occurs while rock is in solid state
* 100-900 degrees celsius

Tectonic Settings of metamorphism

occurs at convergent plate boundaries

fracking and fuel supply

Shale gas obtained, accounts for 67% of natural gas production and 50% of petroleum production in the U.S.

Pros and cons of fracking

provides cheap energy, but pollutes the environment

Mineral

a naturally occurring inorganic element or compound having an orderly internal structure and characteristic chemical composition, crystal form, and physical properties

Rock

* a natural substance composed of solid crystals of different minerals that have been fused together into a solid lump
* a solid mass composed of one or more types of mineral

Crystallization

* a natural substance composed of solid crystals of different minerals that have been fused together into a solid lump
* a solid mass composed of one or more types of mineral
* The process of liquid rock freezing into solid rock

Crystal

* a solid that has a highly ordered, repeated microscopic structure
* can remain microscopic, or grow to form large macroscopic crystals
* the largest documented on Earth are of beryl (Be3Al2Si6O18) located in Madagascar. They measure up to 18m long and weigh 380 tonnes

Types of crystal structure

Crystalline, polycrystalline, amorphous

Crystalline

* solids have well-defined edges and faces, diffract x-rays, and tend to have sharp melting points
* regular order extends over the entire crystal

Polycrystalline

* regular order only exists over a small region of the crystal

Amorphous

solids have irregular or curved surfaces, do not give well-resolved x-ray diffraction patterns, and melt over a wide range of temperatures

Halite Crystal

Rock salt, cubic

Crystal shapes

cubic kubish, tetragonal, hexagonal trigonal, rhombic rhombisch, monclinic monoklin, triclinic triklin

the 2 step of crystal formation

Nucleation, growth

Nucleation

* when molecules or atoms dispersed in a solution come together into microscopic clusters
* In chemistry (or cooking) a nucleation site can be introduced to a solution in order to “skip” this step. This provides the “seed” for crystal growth

Growth

* The nucleus acts as a converging point for molecules to attach to, and assemble in successive layers (like an onion)

5 factors that affect rate of crystal growth

* Concentration of solution


* Temperature
* Pressure
* Crystal surface area
* Flow rate

Formation of mineral crystal

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* Elements needed must be present in the appropriate proportions
* Physical and chemical conditions must be favourable
* Needs sufficient time for the atoms to become arranged


* Minerals / crystals can also form in nature from supersaturation (e.g. evaporites)
* Can also form biologically

4 mineral classes in rock

Silicates, oxides, sulphides and sulphates

Silicate minerals

* Silicon and oxygen combine with each other and with other elements to form silicate minerals
* Ninety-five percent of continental crust is formed from silicate minerals
* Feldspar is the most common type of mineral in Earth’s crust—mostly found in ocean crust
* Quartz is one of the most abundant minerals on land

Non-silicate minerals

Halides, oxides, sulphides and carbonates

Halides

Sodium chloride or rock salt

Oxides

Hematite- gives many rocks a reddish colour

Sulphides

Pyrite, also called “fool’s gold”

Carbonates

Calcite- often bonds sand grains together

Rocks

Most rocks are an assemblage of many minerals **cemented** or interlocked together

Sediments

accumulations of small fragments of rock and organic material that are **not cemented** together

Bedrock

rock that is structurally part of Earth’s crust

Outcrops

exposed areas of bedrock

* Most common in mountains
* There are a few outcrops in flat interior regions

Igneous rocks formation

form when magma or lava solidifies

Sedimentary rocks formation

form through cementation and compaction of sediments

Metamorphic rock formation

Form by heat and pressure applied to preexisting rocks

Metamorphic rock groups

* foliated
* non-foliated

Foliated metamorphic

* flat or wavy banding patterns that may superficially resemble sedimentary layers but are unrelated to them in how they are formed
* extremely __**high pressures**__ that are __**unequal**__, occurring when the pressure is greater in one direction than in the others (directed pressure)

Cleavage

As the rock is squeezed under great pressure, minerals in the rock may become flattened and aligned, creating a grain to the rock also known as ____.

Non-foliated

* metamorphic rocks that are formed under high temperature, and __**LOW PRESSURE equally**__
* They have little or no structured grain pattern or mineral alignment and usually lack any banded or layered appearance

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The rock cycle gist

1. form when magma cools and hardens into rock from a molten state, either deep within Earth’s crust or at a volcanic vent (igneous rocks)
2. After rocks harden, they are subject to weathering . . . fragments are deposited as sediments

First step in the rock cycle

New igneous rock

* magma cool deep within the crust
* Lava cools on the crust’s surface
* both magma and lava from igneous rock

Second step in the rock cycle

Weathering and erosion

* Through the process of weathering, igneous rocks are broken down into smaller fragments and chemically altered as they interact with water, sunlight and organism
* Streams, wind, and ice transport the sediments downslope

Third step in the rocks cycle

New sedimentary rock

* sediments are deposited and accumulate in river floodplain, in coastal regions, and on the seafloor
* through compaction and cementation, the sediments may be lithified (turned to rock), forming new sedimentary rocks

Fourth step in the rock cycle

New metamorphic rock

* sedimentary rocks may be compressed and heated in subduction and collision zones, forming metamorphic rocks

Fifth step in the rock cycle

Recycling

* rocks can be subducted deep into the mantle and become a part of the mantle
* If they are instead melted, they form rising bodies of magma that migrate up toward the surface, where they eventually cool into new igneous

Cementation

the process in which minerals, such as calcite, fill the spaces between sediment particles and bind them together to form sedimentary rock

Lithification

the transformation into rock

Igneous rocks

* form when hot, molten rock crystallizes and solidifies

Decompression melting

* the melting of hot mantle material into magma as a result of pressure changes

Decompression occurs in 3 tectonic setting

* mid-ocean ridges
* rift valleys
* hot spots

Flux melting

the process by which subducted water causes mantle material to melt by lowering its melting point

Decompression melting and flux melting

both result in production of magma, which contributes to building crust when it cools and hardens into new igneous rock.

Igneous rock groups

* Phaneritic rocks
* Aphanitic rocks
* Glassy rocks

Phaneritic rocks

Coarse-grained rocks with large crystals that formed slowly deep in the crust

* Large crystals
* plutons and batholiths

Aphanitic rocks

rocks that cool more quickly closer to the surface

* very small crystals not visible without magnification
* laccoliths and dikes are composed of

Glassy rocks

no orderly crystalline arrangement of atoms because they cool rapidly at the surface

Felsic rocks

* Also called granite rock
* about 75% silica
* light in colour
* less dense than mafic
* igneous

Mafic rocks

* Also called basaltic rocks
* about 50% silica

Bowen’s reaction series

describes the temperature at which minerals crystallize when cooled, or melt when heated

Sedimentary rocks layer

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* Each layer of sedimentary rock is like a page from the book of Earth’s history, it records the environments existing at the time of its formation

Sedimentary rock groups

Clastic, organic, chemical

Clastic sedimentary rocks

composed of broken pieces of other rocks

Organic sedimentary rocks

composed mostly of organic material derived from ancient organisms or their shells

Chemical sedimentary rocks

formed as dissolved minerals precipitate out and as water evaporates from sedimentary deposits

Examples of clastic sedimentary rocks

Claystone, shale, siltstone, mudstone, sandstone, conglomerate

Igneous and metamorphic rock portions

Portion of the crust: 96%

Portion exposed at the surface: 25%

Sedimentary rock portions

Portion of the crust: 4%

Portion exposed at the surface: 75%

Examples of organic sedimentary rocks

Fossiliferous limestone, chalk, bituminous coal

Examples of chemical sedimentary rocks

Rock salt (halite), gypsum, limestone/ tufa

Shale

* a clastic sedimentary rock formed from clay-sized particles
* 45% of all sedimentary rocks

Sandstone

* a clastic sedimentary rock composed chiefly of quartz sand grains
* 32% of all sedimentary rocks

Limestone

* either a chemical sedimentary rock or an organic sedimentary rock
* 22% of all sedimentary rocks

Protolith

the parent, or original rock

Metamorphic rock classification by size

slate (small) , schist (intermediate), gneiss (large)

Metamorphic rock classification by chemical composition

marble (Calcite), quartzite (quartz), anthracite coal (carbon)

Active Volcano

a volcano that has erupted in the past 10,000 years and could erupt again

Extinct volcano

a volcano that has not erupted for tens of thousands of years and can never erupt again

Effusive eruptions

a nonexplosive eruption that produces mostly lava

Explosive eruption

a violent eruption produced by a stratovolcano in which pyroclasts are ejected high into the atmosphere

* caused by thicker magma, more silica content, gases become trapped in magma building up to erupt in a potentially explosive way

Magma

molten rock underground

4 ways scientists predict eruptions

1. scientists take gas samples to understand how magma is moving beneath the ground
2. scientists measure surface cracks. Widening of cracks could indicate that magma is rising up through the magma chamber
3. Seismic stations on the volcano measure earthquake activity
4. scientists measure surface swelling from a distance

Lava

Molten rock that breaks through Earth’s surface

Four types of volcanos

Shield, strato, cinder and lava

Shield Volcanoes

* doomed volcano
* formed from innumerable layers of fluid __**basaltic lava**__ laid down over tens to hundreds of thousands of years

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* Largest
* Slowly built as magma travels up from magma chamber and through the volcanic vent

Magma chamber

The reservoir of magma beneath a volcano

Volcanic vent

the conduit through which magma moves and reaches the surface

Stratovolcano

* Also called composite volcano
* Potentially explosive, cone-shaped volcano composed
* formed of alternating layers of lava and pyroclasts