Geology 100 Final Exam Review

	Geology 100 Introduction to Geology

FINAL EXAM REVIEW

Overview

The Final exam covers: Text Chapters 1-4; 7-12 & 14-15
It consists of 75 multiple-choice & true/false questions

Remember the Introductory Lecture from the beginning of the semester is another good study tool for your final exam.

Chapter 1: Introduction to Physical Geology

Benefits of Geology

The field of geology helps us to understand our surroundings; supplies us with natural resources; protects our environment and assists us in avoiding geologic hazards.
The study of geology is based on scientific method which believes that by objective analyzing of phenomena we can discover their workings.
One of the great contributions to human understanding made by geology is the concept of the vastness of geologic time.

Theory of Plate Tectonics

The theory currently accepted as to the workings of the Earth is called plate tectonics . It is largely accepted by the scientific community because it accounts for a greater range of observed phenomena than any other theory.
The theory is basically simple: it states that the crust and upper mantle of Earth are in constant motion, slipping on a partially molten layer called the asthenosphere.

The Earth Engines

The Earth has two engines- an internal engine propelled mostly by temperature differences within the earth's mantle caused by heat from decay of radioactive minerals . This engine builds up the earth.
And an external engine powered by the sun and gravity which causes the hydrologic cycle, weather patterns and ocean currents. The external engine ultimately weathers and erodes the Earth.
Through these two engines the Earth is seeking equilibrium.

Uniformitarianism

An 18th C Scotsman, James Hutton was the first to propose that geological time was vast. His hypothesis was that the geological processes of the past could be explained by the same processes he observed taking place around him.
This has become known as the principle of uniformitarianism and has been paraphrased as "the present is the key to the past".

The Age of the Earth

About 70% of Earth's surface is under water. The source of water is from within the Earth, emitted from volcanoes and vents of the early, still hot and steaming planet during a process called degassing
By dating meteorites and moon rocks it is estimated that our solar system began to form about 4.6 billion years ago. From these studies it is estimated that the Earth formed approximately 4.5 billion years ago.
From the time of formation until the appearance of the first abundant fossils at approximately 545 million years is Precambrian Time.
Precambrian time is followed by the Cambrian Period of the Paleozoic Era. During the Cambrian Period we see the first abundant fossils, especially trilobites, which are a index fossil of this period.
Have a general idea about the Eras and their approximate dates.

Chapter 2:The Interior of the Earth

Geophysics: Heat

The deep internal parts of the Earth are studies indirectly, thru geophysics. Geophysics studies seismic waves, the earth's magnetic field, gravity and heat. Together these help us get a clear picture of the Earth's interior.
Remember heat gradient is the heat increase as one moves deeper below Earths surface, whereas heat flow is the loss of heat through the Earths surface. The heat flow from the continents is the same as that from the ocean crust.

Geophysics: Gravity

The force of gravity between two objects varies with the mass of the objects and the distance between them.
This means that the greater the mass or density and the closer objects are to one another, the greater the force of gravity.

Geophysics: Magnetic Field

A magnetic field surrounds the Earth. The strength of the magnetic field is greatest at the magnetic poles.
It is thought the Earth's magnetism might be generated within the liquid outer core by circulating electric currents.
When the polarity of the Earth's magnetic fields changes it is called magnetic reversal. Many rocks contain a record of the strength and direction of the Earth's magnetic field at the time the rocks were formed- stacked lava flows are an example.

Geophysics: Seismic Waves

Studies of seismic waves have shown (1) that the earth's crust is thinner beneath the oceans than it is beneath the continents and (2) that seismic waves travel faster in oceanic crust than in continental crust.
This velocity difference, indicates that the oceanic crust is denser and that the two types of crust are made of different rock.
The oceanic crust is primarily made up of basalt, while the continental crust is primarily made up of granite.

Parts of the Earth: Crust

The crust is a thin layer on the surface of the Earth. There are two types of crust-continental and oceanic. The differ in density, composition and the way they are formed.
Oceanic crust is thinner and somewhat denser than the continental crust.

The Principle of Denseness

Dense- Particles closely packed. Something dense is heavier and contains more mass than something less dense of equal size.
Are dense and thick the same thing? No, some of the thickest crust is less dense. The thickest crust is beneath mountain ranges especially geologically young mountain ranges i.e. the Andes and Himalayas.

Parts of the Earth: Mantle

The mantle is the largest by volume and contains most of the earth's mass. It lies between the core and the crust. There is an upper and lower mantle.
The mantle is solid except for in a few spots and probably is composed of ultramafic rock. Ultramafic rock is heavy igneous rock made up chiefly of ferromagnesian minerals which lack feldspar.
The crust and uppermost mantle are rigid and make up the lithosphere .
The boundary in the lithosphere between the crust and the mantle is called the Moho or Mohorovicic discontinuity.
The upper mantle which underlies the lithosphere to a depth of 200 km is the asthenosphere. Seismic waves slow here, so we believe the asthenosphere is partially molten and behaves plastically.
Convection is believed to take place within the asthenosphere as well as in the rest of the upper mantle and lower mantle. This convection (internal heat engine) powers the movement of the rigid lithosphere over the asthenosphere in the theory of plate tectonics.

The Mantle and Isostasy

Isostasy is a balance between adjacent blocks of crust floating on the plastic upper mantle. Crustal rocks weigh less than mantle rocks (they are less dense) so crust floats on the mantle, like a block of wood on water. Like wood, the crust displaces the mantle.
The high mountain ranges have a thick crust that descends deep into the mantle (like deep roots). The crust is the thinnest and the mantle the thickest where the ocean is deepest- i.e. trenches
Think of it like an iceberg. The bigger the visible part the deeper it goes.
Erosion and deposition produce the loss and gain of mass which causes parts of the Earth to constantly adjust to reach equilibrium.
Crustal rebound is an example of equilibrium. When a glacier melts and there is no longer a heavy burden on the land, the land will rise.

Parts of the Earth: Core

The core is the central zone of the Earth. Study of meteorites, the earth's density, seismic studies and the earth's magnetic field point to a metallic core which is very dense and has two parts- a solid inner core where high pressure prevents any liquification . And a molten outer core. The core is thought to be composed of iron and either sulfur, silicon, or oxygen.

Chapter 3:The Sea Floor

The Sea Floor

The rocks and topography of the sea floor are different from those on land. They are formed from different geological mechanisms than those on the continents. The geological structures on the ocean floor have a much larger scale and different composition than those on the continents.
Ocean scientists have learned that the water in the oceans is very ancient, formed perhaps 4 billion years ago but the oldest rocks on the sea floor are about 200 million years old.

Mid-Oceanic Ridges

The mid-oceanic ridges , are volcanic mountains that are dominant features of every ocean basin.
They are composed of black igneous basalt (pillow lava).
These mountains are interconnected and are the greatest mountain ranges on Earth.
The one place where the mid-oceanic ridge comes above the surface of the ocean is Iceland, where the divergent plate boundary allows for geothermal energy.

Chapter 4: Plate Tectonics

Plate Tectonics

The Earth's surface is divided into a few large, thick plates that move slowly and change in size. There are 8 large plates and a few smaller plates.
The plates move apart or diverge, come together or converge or they move along transform boundaries.
North American plate and the Pacific plate effect us in California along the San Andreas fault, a transform boundary.
Plate tectonics combines Alfred Wegener's theory of continental drift and Harry Hess' theory of sea floor spreading.

Wegner

Wegener's continental drift theory maintained that the continents move freely over the Earth's surface plowing over a stationary sea floor.
A supercontinent called Pangaea probably formed long ago by the collision of smaller continents.
About 200 million years ago Pangaea broke up into 2 parts- Laurasia, the northern supercontinent containing what is now North America and Eurasia (excluding India) and Gondwanaland, the southern supercontinent composed of all the present day southern hemisphere continents and India.

Vine and Matthews

This theory of sea floor magnetic anomalies allows us to measure the rate of sea floor motion (which is the same as plate motion since they move together as plates).
Since magnetic reversals have already been dated from lava flows on land, the anomalies caused by magnetic reversals can also be dated telling us how fast the sea floor has moved. Another important point of the Vine and Matthews hypothesis is that it predicts the age of the sea floor .

Types of Plate Boundaries: Divergent

Plates move apart, can occur in the middle of the ocean or in the middle of a continent. The mid-oceanic ridge is one example.
Features of a continent breaking up: Area is elevated because of rise in hot mantle rock. Tensional cracks, shallow focus earthquakes and a rift valley forms. Continental crust on upper part of the plate clearly separates and sea water may flood in. Rise of magma forms oceanic crust between the two diverging continents; a new ocean is formed.

Types of Plate Boundaries: Ocean-Ocean Convergent

Move toward each other, & have different characteristics depending upon the types of plates that converge.
Ocean-ocean convergence- plate of oceanic crust moves toward another plate of oceanic crust, the older, more dense plate subducts under the other plate.
An oceanic trench is formed. If subducting plate reaches the asthenosphere andesitic magma forms and works upward to erupt as an island arc. If subduction angle is gentle and the plate does not melt, there will be no volcanic island arc.

Types of Boundaries: Ocean-Continent Convergent

Dense oceanic crust subducts under the continental crust forming a deep sea trench parallel but offshore to the continental margin.
Subducted oceanic rock and part of the continental crust undergo partial melting to produce the andesitic volcanoes which form young mountain ranges.
In either O-O or O-C Convergence, when plates subduct the boundaries are marked by trenches, low heat flow, Benioff Zones, andesitic volcanism and young mountain ranges or island arcs.

Types of Plate Boundaries: Continent-Continent Convergent

Continent-continent convergence-Two continents approach each other and collide. Initially separated by a subducting ocean floor they lack a spreading center to create new oceanic crust.
When they collide one continent may slide a short distance under the other along the subduction zone but it is not dense enough to subduct.
The two continents are welded together along a suture zone that marks the old site of subduction. The result is a mountain range in the interior of a continent. Shallow focus earthquakes may occur along numerous faults.

A Quick Quiz

Is a valley divergence or convergence? Divergence, examples- mid-oceanic rift & the African Rift Valley.
Are andesitic volcanic mountains or island arcs, divergence or convergence? Convergence, examples- Andes Mountains & Philippine Islands.
Is Iceland an example of divergence or convergence? Divergence it is the only place where the mid-oceanic ridge comes above the ocean surface.
Are the Hawaiian islands an example of divergence or convergence? Neither, they are formed by mantle plumes/hot spots.

Types of Plate Boundaries: Transform

Transform boundaries, where one plate slides horizontally past another along a single fault or group of parallel faults, are marked by shallow-focus earthquakes.
In California we are very familiar with the San Andreas fault in which the North American Plate and Pacific Plate slide past each other.

Chapter 7:Earthquakes

Earthquakes

An earthquake is a shaking of the ground caused by the release of energy stored in the rocks beneath the earth's surface.
When a rock breaks waves of energy called seismic waves are sent through the earth. The vibrations or seismic waves originate at the focus, a point within the earth on a fault where the movement or first release of energy takes place.

Seismic Waves: Surface waves

Surface waves ( Love and Rayleigh waves) travel on the Earth's surface.
Surface waves are the slowest and most damaging because they create the greatest ground motion. Dont worry about the types of surface waves.

Seismic Waves: Body Waves

Body waves (P & S waves) travel through the Earth's interior. Know the difference - the fastest highest frequency waves are P waves (primary, push-pull waves, like a slinky). They are transmitted through air, liquids and solids. The S waves (secondary, slower, shake), are transmitted by solids only.
The P, S and surface waves all originate at the point of focus at the same time. Because of the difference in speed at which the waves travel, they reach seismographs in a definite order.

Chapter 8: Time and Geology

Uniformitarianism Again

Remember: the concept of the immensity geologic time is one of the most significant contributions to human thought made by the science of geology . An understanding of the enormous scope of geologic time is basic to our understanding of geologic phenomena i.e. plate tectonics.
The modern concept of geologic time began with James Hutton and the principle of uniformitarianism. The idea that ancient landscapes were formed by processes which are in operation today. In other words the present is the key to the past, although the rate of certain geologic activity and the sites of geologic activity have changed.

Relative vs Numerical/Absolute Time

Geologists are usually more concerned with relative time/age the sequence in which events took place, than they are with the number of years involved- what they call numerical or absolute time/age.
Numerical time is determined via radiometric/isotopic dating.
Contacts, are the surfaces separating two different rock types or rocks of different ages. Contacts are particularly useful in determining the geologic history of an area.

Numerical/Absolute Time

Has been determined since the discovery of radioactivity. Oldest rocks found on earth are in Northwestern Canada and are about 3.964 billion years old.

4.5 billion year estimated age of the earth is from various evidence that all the planets formed about this time.
We can determine the age of rocks because we can measure the rate of radioactive decay.
Radiometric (isotopic) dates support the relative time scale.

Principles to Determine Relative Time

Remember: Relative Time is a sequence of events. The determine RT we use the following-

Original Horizontality- layers are laid down in a horizontal fashion
Superposition- layers on the bottom of the pile are older than those on the top.
Lateral Continuity-sedimentary layers extend laterally until they taper or thin at the ends
Cross Cutting Relationships- any break or intrusion is younger than the layers that are broken or intruded into

Fossils

Fossils are common in marine sedimentary rocks and have proved to be of great value in correlating strata and in determining the relative age of layers in which they are found.
Fossils are especially useful in correlating widely separated areas, even different continents.
Ideally geologists hope to find an index fossil- a fossil of a very short lived, geographically widespread species, known to exist during a specific period of geological time.

Geological Time Scale

eons, made up of several eras and three main eras. The eras in turn are divided into periods, which in turn are divided into epochs .

Precambrian denotes the vast amount of time that preceded the first and oldest era, the Paleozoic Era. Rocks in Precambrian time have few fossils.
The Paleozoic Era began about 545 million years ago. In this Era we start to see fossils of abundant and complex life that continue thru all the eras thereafter.
The Mesozoic Era came next. In this middle era, which began 245 million years ago, life on land was dominated by reptiles.
We live in the Holocene or recent epoch of the Cenozoic Era. The Cenozoic Era began about 66 million years ago and is known as the age of mammals.
The boundaries between the eras represent major changes in the fossil records such as mass extinctions and the appearance of many new life forms

Chapter 9:Atoms, Elements and Minerals

Elements and Atoms

An element is a substance that cannot be broken down by ordinary chemical methods. Elements are basic substances, each made of its own kind of atom. Oxygen, silicon and aluminum are the three most common elements on the earth's surface. An atom is the smallest part of an element that retains the properties of that element.
All materials are made from atoms that are composed of sub-atomic particles called protons, neutrons and electrons.

Bonding

If the number of electrons equals the number of protons then the negative and positive charges balance and the atom is electrically neutral. Most elements are not able to maintain electrical balance and therefore react or combine with other atoms to achieve a balance.
An electrically charged atom is called an ion. Ionic bonding occurs when positive and negative ions are attracted to one another. It is the most common type of bonding in minerals. Covalent bonding happens when electrons are shared.

Physical Properties

Characteristic physical properties are the basis from which most minerals are identified. Of these, cleavage, the ability of a mineral to break along preferred planes, is one of the most useful diagnostic tools because it is identical for a given mineral from one sample to another. Mica is an example of a mineral with perfect cleavage along one plane.
Stenos Law is also a helpful physical property- all crystals of the same substance have the same interfacial angles.

Chapter 10: Volcanism and Extrusive Rocks

Magma\Lava Composition

A strong correlation exists between the chemical composition of the magma (lava) and the violence of an eruption.
Magma (molten rock that is mostly silica) that works its way to the surface is called lava. Surface rock resulting from volcanic activity is called extrusive igneous rock.
Whether eruptions are explosive or quiet is largely determined by two factors: 1) the amount of gas in the magma and 2) the ease or difficulty with which the gas escapes to the atmosphere. Most of the gas released during eruptions is water vapor which condenses as steam. The viscosity or resistance to flow of lava determines how easily the gas escapes.
Mafic rocks are silica poor. They tend to be dark in color- most common mafic rock is basalt. Gabbro is an intrusive igneous rock that is also mafic.
Felsic rocks are silica rich. They tend to be light in color- Rhyolite is a extrusive igneous felsic rock. Granite is the most common felsic rock and it is intrusive igneous.
Intermediate rocks are in between mafic and felsic. They tend to be gray or green in color- Andesite is extrusive igneous and diorite is intrusive igneous both are intermediate rocks.
Mafic lavas, low in silica, flow easily and form gentle volcanoes. Felsic lavas, high in silica are viscous, thick and flow is sluggish and the volcanoes are more violent.

Composite Volcanoes

Composite volcanoes, called stratovolcanoes are constructed of layers of pyroclastics and rock solidified from lava flows.
Built up over long periods of time they are found on the continents in the circum-Pacific belt.
Mostly composed of intermediate materials, andesite is the most common rock. Most of the larger better known volcanoes of the world are composite volcanoes.

Volcanic Domes

Volcanic domes are masses of volcanic rock formed from viscous lava that solidifies above a volcanic vent. Some of the most destructive volcanic eruptions known have been associated with volcanic domes.
The lava solidifies in the volcanic vent, blocking the gas/steam from escaping like a cork in a champagne bottle.
Ultimately, rock gives way under the pressure and a huge explosion results, i.e. Mt. Saint Helens

Summary of Igneous Rock Types

Mafic	Intermediate	Felsic
Silica Poor: 50% or less	Medium Amount of Silica	Silica Rich: 70% or more
Dark Color	Gray or Green	Light Color
Extrusive Igneous Rock Example: Basalt Intrusive Igneous Rock Example: Gabbro	Extrusive Igneous Rock Example: Andesite Intrusive Igneous Rock Example:Diorite	Extrusive Igneous Rock Example: Rhyolite Intrusive Igneous Rock example:Granite

The Rock Cycle

Sedimentary, Metamorphic & Igneous are the three major types of rock
All rocks start as sediments, bit and pieces of all rock types which pile up and w/ heat & pressure create sedimentary rock.
As heat & pressure increase the rock recrystallizes but does not melt thus creating metamorphic rock.
As heat and pressure increase the rock finally melts when this magma lithifies it is igneous rock .
Igneous rock and all the others erode into sediments starting the process over once more.

Chapter 11:Igneous Rocks, Intrusive Activity and the Origin of Igneous Rocks

Intrusive Rocks

The major difference between extrusive and intrusive igneous rocks is where they solidify- on the Earths surface or within it.
Intrusive rocks appear to have crystallized from magma emplaced in surrounding rock.
Intrusive rocks are usually coarse grained because they form under the Earth's surface and take a long time to cool.
Bodies of intrusive rocks are exposed to us only after erosion and, usually uplift.

Country Rock

The country rock is an accepted term for any older rock into which an igneous body is intruded.
The country rock adjacent to intrusive rock is seen to have been baked or metamorphosed along the contact with the intrusive rock.
This has been caused by the transfer of heat from the igneous rock to the country rock.

Intrusive vs Extrusive Igneous Rocks

Intrusive rocks are the builders of the continental crust and mountain belts.
Extrusive rocks are the volcanics that created the oceanic crust.
Granite (intrusive) is the igneous rock most common on the continents, basalt (extrusive) is most common on the ocean floor, and andesite (extrusive, usually on or near continental margins) is the building material of young volcanic mountain ranges.
A coarse grained texture is the most significant difference between plutonic (intrusive) rocks and extrusive rocks which are likely to be fine-grained.

Ultramafic Rock

Ultramafic rock is composed entirely or almost entirely of ferromagnesian minerals.
No feldspars or quartz are present. Most have less than 45% silica.
Since they are all formed in the mantle rather than on the surface, Ultramafic rocks do not have a fine-grained (extrusive) counterpart.

Bowens Differentiation

Only three major families of magma exist (mafic, intermediate and felsic), but there are literally hundreds of different kinds of igneous rocks.
Norman L. Bowen found a way for both felsic and mafic rocks to form from a single basaltic (mafic) parent magma, this explained the vast array of igneous rocks.
His experiments involved differentiation a process by which different ingredients separate from an originally homogenous mixture. An example is the separation of whole milk into cream and skim milk.

Chapter 12:Weathering and Soils

Weathering

Weathering refers to the group of destructive processes that change the physical and chemical character of a rock at or near the earth's surface.
Weathering breaks down rocks that are either stationary or moving.

Mechanical Weathering

Mechanical weathering, changes the rock physically- there is little or no chemical change. Mechanical weathering can increase the rate of chemical weathering by increasing the surface area exposed to the elements

Chemical Weathering

Chemical weathering decomposes the rock principally by exposure to air and water vapor, to form new chemical compounds which are stable in the surface conditions of the earth.
The most effective agent of chemical weathering is acid.

Soil Development

Clay minerals and quartz, two minerals usually remaining after complete weathering of rock because they are the least reactive, have important roles in soil development.
Layers of soil distinguishable by their physical or chemical characteristics are termed soil horizons.
The O Horizon is the uppermost layer that consists of nondecomposed and highly decomposed organic matter.
The A horizon, forms just below the surface layer of vegetation. This layer contains decomposed plant material or humus, and contributed to the leaching in the E Horizon.
The E horizon or zone of leaching is characterized by a downward leaching of water.
The B horizon, or the zone of accumulation, accumulates the material, often clay, that is leached downward. In humid climates the B Horizon includes clay, iron oxides and calcite.
The C horizon is below the B horizon and is the transition between the unweathered bedrock and the developing soil above.
Over long periods of time the type of parent rock that produces a soil becomes less important. Given enough time soils will become quite similar in the same climate.

Chapter 14: Sediments and Sedimentary Rocks

Types of Sedimentary Rocks

The different types of sedimentary rocks are called respectively, clastic, chemical and organic rocks.

compaction and cementation of sediments is called clastic.

Sedimentary rock formed from precipitation from solution is called chemical

Sedimentary rock can also be made of consolidation of the remains of plants and animals- this is called organic.

Lithification

The general term for the group of processes that change loose sediments to sedimentary rock is lithification.
Lithification involves compaction, cementation or crystallization from solution.

Types of Sedimentary Rocks: Clastic, Chemical and Organic

The most common type of sedimentary rock is clastic sedimentary rock.
In clastic sedimentary rocks sediment grains that are fragments of preexisting rocks are compacted &/or cemented together.
When sediments first deposit some have a fairly large space between the grains. As more sediments pile up the overburden packs the grains closer together, reorienting the particles to each other causing them to join. This is called compaction.

Clastic Rock: Detail

Sand grains tend to be fairly well compacted when deposited. As water moves through the small pore spaces cement can precipitate and bind the grains together. This is called cementation.
Cementation is the primary factor in the formation of sandstones, conglomerates and breccias. Clastic rocks are identified by their grain size. Examples include from small grain size to large: shale[ made from clay], sandstone[ made from quartz sands], conglomerate [made from gravel] and breccia [made from angular gravel]

Chemical Rock: Detail

The second type of sedimentary rock is chemical.
Chemical sedimentary rocks are rocks formed by precipitation from solution- also called crystallization.
Examples include: Rock salt formed when sea water evaporates. Carbonate rocks like Tufas precipitated from high calcium carbonate concentrations in Mono Lake and like the Limestone formed directly as a solid rock by the precipitation of calcite within a coral reef by corals and algae.

Organic Rock: Detail

The third type of sedimentary rocks is organic.
Organic sedimentary rocks are rocks made from the compaction or consolidation of plant or animal material.
Example: Coal or limestone like coquina limestone where the actual shells of sea creatures form the rock.

Environment of Deposition

An important job of geologists studying sedimentary rocks is to try to determine the ancient environment of deposition [the location in which deposition occurred].
Generally sediment deposits get thinner as you move away from their source.
Sorting involves separating various sized grains from one another and depositing like sized particles together. Sediments are well sorted by rivers, but not by glaciers. Glacial deposits are an unsorted mix of boulders, etc.

Chapter 15:Metamorphism, Metamorphic Rocks and Hydrothermal Rocks

Metamorphic Rocks

Metamorphic rocks make up 27% of the earth's crust and yet never have been observed in the process of formation.
Metamorphic rocks are seen only when mountain belts are uplifted, deeply eroded and their ancient roots are exposed to view.
Metamorphic rocks form from preexisting rocks which are transformed into texturally or mineralogically distinct new rock as a result of deep burial, tectonic forces (high pressures) and high temperatures.

Contorted Banding

Since no one has ever observed the formation of a metamorphic rock, why are we lead to believe that metamorphic rocks form in a solid state, i.e. without melting? Many metamorphic rocks exhibit contorted banding.
Because high pressure as well as temperature is required to make rocks plastic [ the ability for the rock to bend in a solid state], it is reasonable to conclude that these rocks formed at a considerable depth. If the rocks had become melted, the banding would have been destroyed.

Types of Metamorphism

There are two types of metamorphism- contact or thermal and regional or dynamothermal.
Contact metamorphism occurs where high temperatures are dominant and pressure is not a strong factor. Intense heat required for this process usually comes from magma intruding into the country rock via sills, dikes etc. and baking the rock.
Rocks formed this way are nonfoliated, i.e. there are no parallel alignments or planes of the minerals in the rock.

Regional Metamorphism

Regional metamorphism is caused by high temperature and differential stress and/or direct and confining pressure.
The majority of metamorphic rocks found on the earth's surface are of this type. These rocks are foliated. They split into parallel alignments or planes-which makes them poor to build on.
Know that nonfoliated rocks (contact metamorphism) are named by the rock's mineral composition. Whereas foliated rocks (regional metamorphism) are named by texture & the kinds of foliation, regardless of the composition of the rock.

Progressive Metamorphism

With progressively greater pressure and temperature during regional metamorphism- one rock type will change to another, i.e. shale will change first to slate, to phyllite, to schist and at the highest temperatures and pressures to gneiss. This is called progressive metamorphism

Metamorphic Facies

A metamorphic facies is a group or assemblage of minerals that formed in response to a specific environment.
The combination of minerals in a rock is the basis for determining the facies to which the rock belongs.
The metamorphic facies group each rock by the combination of temperatures and pressures which represent its stability field.

THE END. I hope that you enjoyed the class!

FINAL EXAM REVIEW