GMOA Notes

This is a work in progress, and eventually I will finish it. Sorry it is taking so long.

These are notes that cover Geology, Meteorology, Oceanography, and Astronomy.

Introduction
Earth's four spheres

Hydrosphere - dynamic mass of liquid that is always on the move
 * Oceans - the most prominent feature of the hydrosphere
 * 71% of Earth's surface is covered by ocean which is 97% of Earth's water
 * Only 3% is fresh water - streams, lakes, glaciers and underground supplies
 * Water Cycle - constantly recycles water

Atmosphere
 * Provides us with the air we breath
 * Protects us from the sun's intense heat and radiation
 * Protects us from space

Biosphere
 * Includes all life on Earth
 * Interacts and influences the other 3 spheres

Lithosphere
 * Earth's rigid outer layer called the crust and the upper mantle called the asthenosphere
 * Solid earth consists of 4 layers:
 * core
 * inner, solid core
 * outer, liquid core
 * mantle
 * lithosphere
 * Divisions of Earth's surface
 * continents
 * ocean basins

Sciences

Sciences involved in better understanding the earth integrate chemistry, physics, and biology into the following sciences:

Meteorology - the study of:
 * the atmosphere
 * weather and climate

Geology - the study of the Earth, and is broken into
 * Physical geology
 * minerals
 * rocks
 * Earth processes - mountain building, earthquakes, volcanoes, etc.
 * Historical geology - Earth's origin and it's past
 * physical
 * biological

Oceanography - study of the Oceans
 * Composition and movement of seawater
 * Seafloor topography and sea life

Astronomy - the study of the universe
 * Earth is a tiny object in a vast universe
 * to understand Earth helps us to understand other planets and vice versa

Resources and Environmental Issues

Environment
 * Physical environment (abiotic)
 * water
 * air
 * soil
 * rock
 * Biological - living environment (biotic)

Resources
 * Important environmental concern
 * Include:
 * water
 * soil
 * minerals
 * energy
 * Two broad categories of resources
 * Renewable resources
 * can be replenished
 * Examples: plant (lumber) and wind energy
 * Nonrenewable Resources
 * Fixed quantities
 * Examples: fuels and metals

Environmental Problems
 * Local, regional, and global
 * Human-induced and accentuated
 * Urban air pollution
 * Acid rain
 * Ozone depletion
 * Global Warming
 * Natural Hazards
 * Earthquakes
 * Landslides
 * Floods
 * Huricanes
 * World population pressures - in 30 years population increased from 4 to 7 billion
 * US makes up 6% of that but uses 30% of the annual mineral and energy resources
 * Alternate energy sources needed

Scientific Inquiry

Scientific Inquiry - scientific knowledge is gained through the following systematic steps called the scientific method, (PI-HE-RAC)

Gather facts through observation then ask why?
 * Problem - state the problem
 * Information about the problem
 * Hypothesis (untested best guess as to why)
 * Experimentation
 * Record and Analyze results
 * Conclusion - accept or reject hypothesis

Goal of science is to discover patterns in nature and use knowledge to predict what will happen under certain circumstances
 * Theory - tested and confirmed
 * Law - no known deviations have ever been found

Minerals
A mineral is a naturally occurring crystalline solid with a definite but not fixed chemical composition and ordered atmomic arrangement.

Chemistry and Mineral Terms

Chemistry Terms:


 * Chemical Property - characteristics of a material, which depends upon how the material reacts with other materials


 * Periodic Table - list of all known elements


 * Element - matter made up of atoms that are essentially all the same and cannot be subdivided by ordinary chemical methods


 * Atom - smallest part of an element


 * Nucleus - central part of an atom made up of protons and neutrons


 * Protons - subatomic particles with a positive charge


 * Electrons - subatomic particles with a negative charge


 * Neutrons - subatomic particles with a charge of 0


 * Atomic number - the number of protons in an atom (above element symbol on periodic table)


 * Atomic mass - the number of protons plus the number of neutrons (below element symbol on periodic table)




 * Isotope - change in the number of neutrons in an atom. Example, and isotope of sodium may have 10 or 12 neutrons


 * Electron Configuration - how the electrons are arranged around the atom in energy levels
 * 1st energy level has 2 electrons
 * all other energy levels have 8 electrons




 * Ion - change in the number of electrons
 * Atoms are most stable with 8 electrons in the outer energy level
 * Will share, lose, or gain electrons to achieve this


 * Ionic bonding - transfer of electrons
 * example - Sodium and Chlorine


 * Lewis Electron Dot Structure - Short hand for showing "chemistry" activity in the outer level by showing the number of electrons in the outer energy level




 * Covalent bonding - sharing of electrons. VERY STRONG BOND
 * example - bond between Hydrogen and Oxygen


 * Metallic bonding - electrons do not belong to any particular nucleus, they float between nuclei
 * example - two metals touching for a long time can "weld" to each other by metallic bonding. You can increase the speed of this by adding heat.

Mineral Terms:


 * A mineral is a naturally occurring crystalline solid with a definite but not fixed chemical composition and ordered atomic arrangement
 * Size of the ion is important because ions that are within 10% of the same size may be substituted in many minerals. This is why minerals of the same type have different chemical compositions.
 * examples - Si,Al; Fe,Mg; Na, Ca


 * Mineral formation
 * Melting - Volcanic activity
 * Evaporation - Salt water: Halite, Gypsum
 * Biological activity - sulfur producing bacteria
 * Oxidized - comes into contact with oxygen: Limonite
 * Leached - as water moves through the soil it dissolves elements. A leech line forms due to mineral formation where the water stops: bauxite
 * Metamorphic processes - formed by heat and pressure. Examples: graphite, chlorite, diamonds. Alters chemical composition and structure, called recrystallization


 * Mineral Types
 * Native minerals - contain one element
 * examples - graphite, C; Copper, Cu; Sulfur, S
 * Sulfides and Sulfates - contain Sulfur and other elements
 * Silicates - contain silicon and other elements
 * Oxides - contain oxygen and other elements
 * Carbonates - contain CO and other elements
 * will effervesce in the presence of an acid
 * Phosphate - contains PO and other elements


 * Physical Property - is controlled by the chemical properties of a material...how its bonded can determine the hardness and the type of impurities that are present in its change in color


 * Color - reflected light; very poor indicator of the true color due to impurities


 * Streak - true color of the mineral found by powdering it. This is found by scratching the mineral across a streak plate.


 * Hardness - the resistance to scratching


 * Cleavage - the tendency for a mineral to break along flat smooth planes that reflect light
 * This is controlled by a weakness in structure, may break where bonds are longer or fewer
 * predictable pattern, not random
 * 1 perfect - stacks like sheets of paper, example: mica
 * 2 perfect - break in two directions and is very clear, example: calcite
 * 3 cubic - breaks into perfect cubes, example: halite
 * none - no repeating faces
 * conchoidal fracture - concentric circles are around breaks, irregular fracture pattern, example: quartz


 * Magnetism - minerals that contain iron and are polarized, example: magnetite


 * Taste - how they taste: bitter, sweet, salty


 * Luster - appearance
 * metallic - look like metal
 * nonmetallic - look earthy


 * Density = mass/volume


 * Specific gravity - how heavy something is in air compared to how heavy it is in water


 * Radioactivity - the breakdown of atoms in the nucleus

Mineral Key
This is not a full table of minerals.

Igneous Rocks and Volcanoes
Rock Cycle
 * the rocks of the crust are classified into 3 types according to their origin
 * Two of the three types are formed by processes deep in the earth's crust and tell us about conditions within the crust
 * There are:
 * Igneous rocks - solidify from a melt or magma. If it cools fast small crystals form, if it cools quickly large crystals form
 * Metamorphic rocks - pre-existing rocks that are changed by heat and pressure within the crust.
 * Sedimentary rocks - weathered rock fragments of older rocks deposited in layers near the earth's surface by wind, water, or glaciers then cemented together by various agents. Records conditions on the Earth's surface.
 * the interactions among the forces that produce these three rock types can be illustrated by the rock cycle.

The Rock Cycle

Igneous Rocks
 * formed by the crystallization of magma
 * magma is a natural, hot melt composed of a mutual solution of rock forming minerals (mainly silicates) and some volatiles (maybe steam), that are held in a solution by pressure. Magma probably originates near the bottom of the crust.
 * magma that reaches the surface before solidifying is called lava.
 * two types of igneous rock
 * extrusive - reach the surface, small crystals, are called volcanic rocks, and cooled on the surface
 * intrusive - doesn't reach the surface, large crystals, called Plutonic rock, cooled below the surface

Volcanism - Volcanic Activity
 * Volcanoes are important because they provide clues about the earth's inaccessible interior.
 * Studying magma, gases and rocks we can determine chemical conditions, temperatures, and pressures within the crust and mantle.
 * Two factors control the violence of volcanic eruptions:
 * The amount of gas in the lava or magma - the greater the amount of gas, the more violent the eruption.
 * Viscosity - the resistance to flow, this determines how easily the gas escapes.
 * Two factors influence viscosity:
 * Temperature
 * Silica Content
 * Gases - most of the gas released from a volcano is steam, which is water vapor. The other gases that are released are Hydrogen Sulfide, Carbon Dioxide, and Hydrochloric Acid.
 * Rocks - chemical analysis shows that silica is the most abundant component in most volcanic rocks.
 * The amount of silica can vary from 45% to 65%. This accounts for the difference in the appearance, mineral content, and behavior of the parent lava.
 * Mafic rocks are silica poor (45% or less silica) and are typically dark in color. The parent lava has a low viscosity.  The minerals included in these rocks are augite, olivine, chromite, and magnetite, which make up dark colored rocks.  The most common mafic rock is basalt.  The lava tends to flow easily (hotter), not as viscous, and is low in silica.
 * Felsic rocks are silica rich (65% or more silica). The minerals included are quartz, potassium feldspar, and muscovite, this produces light colored rocks.  The most common felsic rock is granite.  High in silica, very viscous and explosive.
 * Intermediate rocks have a chemical composition between mafic and felsic. They are medium to dark grey in color.  Andesite is the most common.  Lava is sluggish and explosive.

Volcano Types
 * There are three types of volcanoes that differ in size, shape, and composition.
 * The three types are:
 * Shield volcanoes - mafic in composition, very fluid and nonexplosive magma. The form a broad gently sloping cone (looks like a shield), and are the largest volcanoes on the planet.



This image is from


 * Hawaiian Islands - have quiet eruptions, basalt lava flows from central vent. They are an example of intraplate volcanism, and have formed over a hotspot.
 * Two types of basalt flows:
 * Aa - blocky lava that looks like rubble, cools quickly.
 * Pahoehoe - ropy lava that looks smooth, cools slower than aa.


 * Cinder Cones - very steep slopes of loose rock fragments ejected from the central vent. They are the smallest type of volcano and erode easily.  Mainly made up of pyroclastic material.  Can be found on shield volcanoes.
 * Pyroclastic material or tephra can be any size and is classified by size.
 * Dust, ash - finest particles
 * Cinders - are 2-4mm in size
 * Bombs and blocks - molten blobs become streamlined during flight, solidify, and fall to the ground to form a lens shaped pyroclast.
 * These erode easily and can be found on shield volcanoes.



Cinder Cone Source


 * Composite Volcanoes - also called stratovolcanoes, are made up of alternating layers of andesitic lava and ash. They are the most explosive type of volcano.
 * Lava is very viscous and is felsic in composition which causes the vents to be blocked easily.
 * Plugs cause gas pressure to build up until the pressure is greater that the plug and an explosion results
 * Not as steep as a cinder cone volcano
 * Very violent eruptions
 * Found along converging plate boundaries, which accords to the Theory of Plate Tectonics



Composite Volcano Diagram Source

Calderas
 * a large basin-shaped depression formed by the inward collapse of a volcano after an eruption (example: Crater Lake, OR). They usually exceed 1 km in diameter and fill with rain water or snow melt to form a crater lake.
 * The three stages of caldera formation are:
 * Magma drawn off from eruption
 * No lava weight to support the volcano
 * The volcano collapses inward



Classification of Volcanoes


 * Active - is erupting, has erupted within the past century


 * Dormant - inactive, but has the possibility of being active, there are signs of volcanic activity such as: earthquakes and the smell of sulfur.

Terms
 * Extinct - no longer active, very little chance that it will ever erupt again.


 * Volcanologist - person who studies volcanoes


 * Ring of Fire - Pacific Plate convergence zone along which most active volcanoes are located and many earthquakes occur.


 * Hot Spot - magma chamber close to the surface of a moving plate, formation of the Hawaiian islands is an example.


 * Nuee Ardent - glowing avalanch, turbulent cloud of ash and dust approximately 700 degrees Celsius traveling around 200 km/h, also called pyroclastic flow.


 * Lahar - mud and ash flows, violent mud flow saturated with water. The heat melts snow from the bottom up causing fast and unpredictable movement.


 * Volcanic dome - stiff, blocky lava that extends out of the summit crater, also called the lava dome.


 * Summit Crater - funnel shaped depression marking the top of a lava neck.


 * Vent - opening through which lava erupts (pipe-like conduit), usually called the central vent.


 * Fissure - long narrow vent that lava can flow through.


 * Sill - lava injected between preexisting rock - parallel and concordant.


 * Dike - lava injected between preexisting rock - perpendicular and discordant.

Other Extrusive Rock
 * cooled on the surface
 * Flood Basalts - fissure eruptions, sometimes called feeder dikes. Basaltic lava is very fluid, flows that come to the surface cover extensive areas to a thickness of 3000 to 5000 feet.
 * Pillow basalts (usually on the ocean floor) - caused by submarine eruptions, they are elongate blobs that break out of their thin skin of solid basalt fed from feeder dikes found along the mid-ocean ridge spreading center. The reduction of pressure caused partial melting.

Intrusive Bodies
 * Larger grain size because it cools slowly
 * Mineral composition is the same as extrusive rocks.
 * Country rock - any preexisting rock
 * Types of intrusive bodies:
 * Shallow bodies:
 * Volcanic neck - throat of a volcano exposed by erosion
 * Dike - nearly vertical, sheet-like body that cuts through older parent rock, is perpendicular to the surface.
 * Sill - nearly parallel, tubular body injected along or between older parent rocks.
 * Laccolith - forms lens shaped mass that arches the overlaying strata or land upwards.
 * Deep intrusive rock bodies (Plutons):
 * Batholith - huge, intrusive igneous body, usually greater than 100 square kilometers that was formed when a lava chamber cooled over time.
 * Stock - small dome off of batholith that has been exposed.

Igneous Rocks
 * form from molten rocks
 * two types:
 * Intrusive - plutonic rock which solidifies below the Earth's surface and usually has large crystals.
 * Extrusive - volcanic rock which solidifies above the Earth's surface and usually has small crystals.
 * Igneous rocks are identified by:
 * Composition - 95% of all igneous rocks are in 6 mineral groups.
 * 1) Mica
 * 2) Quartz
 * 3) Amphiboles (Hornblende)
 * 4) Feldspar (Potassium feldspar)
 * 5) Olivine (peridot)
 * 6) Pyroxine (Augite)
 * Textures - three main groups
 * 1) Aphanitic - fine grained, extrusive
 * 2) Porphyritic - combination of crystals, classified by the fine crystals called ground mass, not the larger crystals
 * 3) Phaneritic - coarse texture, large crystals, intrusive
 * Color - light to dark
 * Crystallization temperature - found using Bowens Reaction Series
 * Parent rock - intrusive, phaneritic material that forms extrusive porphyritic or aphanitic rocks.
 * Texture - grain size, not how it feels
 * Glassy textures - cool to fast to contain any visible minerals



Sedimentation and Sedimentary Rocks
Weathering, Erosion, Transportation, and Deposition
 * Weathering - change in the physical or chemical character of a rock
 * Mechanical Weathering or physical disintegration
 * Breaks rocks into smaller pieces from boulders to silt by:
 * Frost wedging and frost heaving
 * Pressure release - unloading a batholith can cause sheeting (cracks parallel to the outer surface) or exfoliation (weathering in layers, like an onion)
 * Plant growth and burrowing animals
 * Extreme temperature change causes contraction and expansion
 * Shape of fragments reveal their history
 * sharp angular fragments burried quickly
 * rounded fragments were transported a great distance
 * Chemical weathering - chemical change
 * original minerals are changed chemically by water and surrounding air.
 * The main reactions are:
 * Oxidation - reaction with oxygen to form an oxide
 * Hydration - reaction with water
 * Carbonation - reaction with carbon dioxide to form a carbonate
 * Other reactions with other compounds are due to rain water composition
 * Bowen's Reaction Series, which shows the sequence of mineral formation also shows the stability to weathering.
 * Erosion, Transportation, and Deposition
 * Erosion is the physical removal of rock by water, wind, glaciers, and ocean waves. Weathering usually helps erosion, but rock can be eroded without any weathering.
 * Water - rain, rivers, and streams
 * Rain washes sediment into rivers and streams, which act as conveyer belts to the ocean
 * The load of the river is broken into 3 parts:
 * Dissolved load - chemical weathering, dissolved into the water
 * Suspended load - fine material carried great distances
 * Bed load - material that rolls or slides on the bottom
 * Flow of a river is determined by:
 * Discharge - the amount of water that passes a point during a certain amount of time
 * Gradient - angle at which the river flows
 * Velocity - the speed of the water which depends on the width of the channel and the amount of friction on the banks
 * Features of Rivers and streams - river valleys are always "V" shaped
 * River erosion deepens, lengthens and widens river valleys. They are "V" shaped because erosion occurs in one place.
 * Distinctive curves called meanders cover the entire flood plain, and were built by sedimentation. Eventually the river will find a new path, and the meanders will become oxbow lakes.




 * Deposition of Rivers and Streams
 * Point Bars - Deposition of sediment on a river or stream
 * Braided Streams - Channels divide and rejoin numerous times and carry abundant loads of sediment
 * Natural Levee - sediment piles up on bank after a flood
 * Delta - river or stream flowing into standing water creates a fan-shaped deposit.
 * Alluvial fan - streams do not reach the ocean and sediment builds up on land. These form where rivers and streams flow out of mountains onto broad, flat plains.
 * Sorting - Rivers sort sediment by size.
 * Dissolved load - chemicals and salts.
 * Suspended load - silt and clay.
 * Bed load - sand and gravel.

Glaciers - thick mass of ice on land formed by accumulation, compaction, and recrystallization of snow.
 * Glaciers form any place where more snow accumulates than melts.
 * Zone of accumulation - snow is added and ice forms.
 * Zone of wastage - zone where there is a net loss to the glacier due to melting
 * Firn limit - area between zone of accumulation and zone of wastage
 * Two major types of glaciers
 * Alpine - form in mountain valleys (also called valley glaciers), will erode "U" shaped valleys in mountains. When one or more alpine glaciers combine they form a piedmont glacier
 * Continental glacier - largest type which covers large portion of the continent (also called ice sheets) and flow out in all directions. Smaller ice sheets are called ice caps.
 * Glacier Features
 * Movement can cause crevasses - open cracks or fisures in ice which extend to a depth of 165 feet. Beyond this depth plastic flow seals them off.
 * Basal sliding - glacier slides or flows as a single body over underlying rock at different rates.
 * Plastic flow - pressure causes plastic movement because the pressure is so great that it moves as a mass
 * Rigid zone - area on top of plastic flow also called the zone of fracture (where crevasses form)
 * Moraine - made of till (mixture of boulders and silt). Large deposits of till can be found:
 * Lateral moraine - deposits on the side of the glacier
 * Medial moraine - deposits in the middle of the glacier after two glaciers flow and join together
 * Terminal or end moraine - deposits at the end of glaciers advance
 * Rock flour - very fine silt in water causes the water to look turquoise or milky.
 * Loess - dry flour, deposits of wind blown silt
 * Glacial erosion - basal sliding carves rocks smooth by "plucking" blocks of rock and carrying them off
 * faceted - flat surface
 * striations - grooves or long scratches in bed rock
 * cirque - steep-sided, rounded-hollow on mountain side, bowl shaped depression at the head of a glacial valley
 * Horn - pyramid like peak caused by cirques on at least 3 sides
 * Arete - sharp edged ridges cut by glaciers on two sides
 * Hanging valley - small valley above larger valley usually marked by spectacular waterfalls

Ocean Processes - most coastal processes are controlled by waves.
 * Waves are formed by:
 * Wind friction on water surface
 * Turbulent water caused by breaking waves is called surf.
 * Size of a wave depends on:
 * Intensity of the wind
 * Fetch - area which the wind is blowing over
 * Length of exposure
 * Depth of the water
 * Parts of a wave include:
 * Wavelength - distance from crest to crest or trough to trough
 * Crest - top of the wave
 * Trough - bottom of the wave
 * Height - top of crest to bottom of the trough
 * Wave motion - water particles within a wave, in deep water, do not move forward with the wave but move in circular orbits.
 * The size of orbits decrease as you move below the surface. At a depth of half the wavelength the wave motion disappears completely.
 * Breaking Waves
 * As the wave moves into water that is half the wavelength deep, the wave starts to drag on the water bottom. This causes the height of the wave to increase and the wavelength to get shorter.  As this continues, the wave becomes unstable and breaks.
 * Waves move sediment by:
 * When the wave drags on the bottom it picks up sediment and deposits it on the beach.
 * Longshore current causes beach drift (also known as longshore drift). If the wave breaks at an angle, it will carry sediment down the shoreline.
 * Longshore drift can cause:
 * Sandspits - elongated ridges of sand that project from the land into the mouth of an adjacent bay or river opening along a coast.
 * Closing of bays - this deposit of sand is parallel to the shoreline and will eventually close off the bay
 * The formation of barrier islands
 * Ways we try to stop longshore drift:
 * Groins - a barrier built at a right angle to the beach to trap sand.
 * Jetties - a pair of structure built extending into the ocean at the entrance to a harbor or river that are built to protect against storm waves and sediment deposition.

Characteristics of Sedimentary Rocks
 * Sedimentary rocks form by lithification of sediment, precipitation of solution, and consolidation of plant and animal remains.
 * This involves:
 * Lithification - compaction and cementation
 * compaction - packs loose sediment together
 * cementation - pore spaces filled with cement
 * Precipitates of solution - crystals grow as water evaporates
 * Classification of Sedimentary Rocks

Metamorphic Rocks and Mountain Building
Metamorphic Rocks
 * rocks of any type or composition that have been changed by heat and pressure while in the solid state, either in texture or mineral composition.
 * The agents of metamorphism are:
 * Heat - the deeper a rock is located within the earth, the more heat it is subjected to.
 * Confining Pressure - The result of burial. At increased temperature and pressure deep in the earth, rocks lose much of their strength and behave plastically.  The pressure is uniform in all directions (similar to when you are submerged in a swimming pool or other body of water).
 * Stress - Directed pressure - the effect of this is to fold the rocks. The more plastic the rock, the more "ductile" it is said to be.  Stress may deform rocks and flatten or stretch pebbles or fossils.
 * Shear - results when rocks are broken and moved by directed pressure. Causes faults.
 * Chemically active solutions - water is generally present in most rocks. Only a thin film on the grain boundaries is necessary.  The water may contain other materials that cause or promote reactions.  This may greatly reduce the rocks strength.  Hot springs (hot water) may cause low grade metamorphism.

Types of Metamorphic Rocks
 * Metamorphic rocks can be subdivided into three groups:
 * Thermal or contact metamorphic rocks - these are generally found at the margins of intrusive igneous rock bodies. These are called hornfels.
 * Regional metamorphic rocks - these generally occupy large areas and form deep in the earth's crust. Significant uplift and erosion has occurred if these are found on the surface.  Regional metamorphic rocks recrystallize under great stress so that new minerals grow in preferred orientation, creating foliation (layering).  Gneiss and schist are common regional metamorphic rocks.
 * Dynamic metamorphic rocks - result from breaking and grinding along faults without much recrystallization.
 * Textural groups of metamorphic rocks are broken into two groups.
 * Foliated - are directional or have a layered aspect to them. The crystals have been aligned into thin layers.
 * Non-foliated - are homogeneous or massive. There are two types of non-foliated rocks which are:
 * Hornfels - rocks next to an igneous intrusion which have been baked (thermal metamorphism).
 * Development of new material from parent rocks.
 * Examples of this are:
 * Limestone to marble, sandstone to quartzite, and talc to soapstone

Prograde and Retrograde Metamorphism
 * Prograde metamorphism - rocks change from lower to higher grade of metamorphism as they are buried deeper and exposed to greater temperatures and pressures.


 * Retrograde metamorphism - rocks change from higher to lower grade of metamorphism as they are pushed up from depth and exposed to lesser temperatures and pressures.

Mountain Building
 * The process that collectively produces a mountain system is called orogenesis from the Greek "oros" (mountain) and "genesis" (to come into being).
 * Crustal uplift - occurs when the crust moves up. Evidence of this:
 * Marine fossils are found at high elevations.
 * Terraces - old sea level platforms cut into the coastline.
 * Isostasy - a floating crust in gravitational balance.
 * Isostatic adjustment -
 * adding weight to the crust makes it respond by sinking.
 * removing weight responds by rising until it is back in balance.
 * Evidence of this - 1) Ice Age Glaciers melted and land uplifted to 330 meters. 2) Mountain summits rise as they erode exposing deeply buried portions (plutons).
 * Mountain Types - no two mountains are exactly alike but can be classified according to their structural characteristics. There are four main categories:
 * Upwarped mountains - arched areas exposing very old cores - example the Black Hills in South Dakota
 * Folded mountains - Alps, Himalayas, Northern Rockies are examples. Although folding is the most conspicuous, faulting, metamorphism, and igneous activity are always present in various degrees.
 * Fault-block mountains - large sections of land are faulted due to:
 * uplift which causes elongation (stretching) and faulting
 * compressional forces which cause overriding (one block over the other).
 * Volcanic mountains - formed by Subduction zones.

Deformation of Rocks
 * Whether a rock breaks or folds depends on its strength and the rate it is deformed. Rock strength depends on the type of rock and the prevailing temperature and pressure.  Ductile rocks tend to fold and brittle rocks tend to fault.  Folding is more common at depth, and faulting is more common near the surface.
 * Folds are formed from directed forces and can be described as:
 * Synclines - basin like folds ("sink"), these form mountains. The youngest rocks are at the center, and folds may be upright, overturned, tight, or open.
 * Anticlines - hill like folds (form an "A"), these form valleys. The oldest rocks are at the center, and can be classified the same way as synclines.
 * Anticlines and synclines are often formed together.




 * Monoclines - buckling and compression




 * Stress - Directed pressure. Stress is a force that deforms rocks.
 * compressional stress - towards each other
 * tensional stress - away from each other
 * shear stress - past each other




 * Strain - the amount of lengthening or shortening of the rock. The amount of strain indicates how much the rock has been deformed.

Faults - break in rock along which movement has taken place.
 * Features of a fault:




 * the block above the fault plane is the hanging wall
 * the block below the fault plane is the footwall


 * Four main fault types
 * Normal faults - hanging wall moves down in relation to the footwall; caused by tension
 * Reverse faults - hanging wall moves up relative to the footwall; caused by compression
 * Strike-slip faults - surface shift; caused by shear
 * Oblique-slip faults - both horizontal and vertical movement; combination of either a normal or reverse fault with a strike-slip fault



Unconformity - break in the geologic record due to erosion and deposition. There are three types of unconformities.
 * Disconformity - New surface parallel to the missing beds; most difficult to detect.
 * Angular unconformity - tilted or folded rock eroded and then covered by younger rock (underlying rock is at an angle).
 * Sequence of events to form an unconformity:
 * Deposition and lithification
 * Tilting or folding of the rocks
 * Erosion
 * New deposition
 * Non-conformity - Plutonic or metamorphic rock eroded and covered by younger sedimentary or volcanic rock.