Surface Processes, Minerals, Rocks and Structural Geology

 

Resources: University of Texas, Arlington; Amethyst Galaries; EdNet; Planetscapes.com; USGS; Volcano World; James Madison University; University of Maryland, Department of Geology; Groundwater.com; Canadian environment; mbgnet (Biomes of the World); USGS (United States Geological Service); USecosystems.org; Pima Community College; Cornell University

 

(Skip to 2.2: Rock Formation)

(Skip to 2.3: Shaping Earth's Surface: Surficial Processes and Features)

 

 

2.1 Tectonic Processes and Features

 

 

1. Evidence for Continental Drift

 

2. Thermal processes driving plate movement

What drives plate movement

 

3. Relationship of density and buoyancy to plate movement

Thermal history of earth gives rationale for plate movement

Structure of the Earth (Earth's Interior) Alternate view

Structure of Earth's lithosphere Relationship to heat of layers of earth

 

4. Location of plates and their direction and speed of motion

CLICK ON MAP TO THE LEFT TO SEE ENLARGED VIEW OF THE PLATES OF THE WORLD AND VOLCANIC HOT SPOTS. Shows names of all plates

Activity: Print the enlarged version of the plate tectonic map to the left. Before you access the absolute plate motion calculator below take a moment and review the meaning of latitude and longitude in the "Review Latitude and Longitude" link. Latitude are the numbers on the horizontal axis and longitude are the values along the vertical axis but you will see this more clearly as you look at the information in the link. You will need that information to get accurate results.

Then click on the absolute velocity calculator link below and calculate the absolute velocity and direction of movement of the major plates of the Earth.

Draw a vector (an arrow with magnitude) representing the speed and direction of movement of each plate. Use a circular or semicircular protractor like the ones to the left to find the direction of the vector and make a scale of velocity and length of vector.

Finally, check the results of your speed on the "Speed of Tectonic Plates" link below.

Review Latitude and Longitude Visually

 

 

 

 

 

5. Major Geological Events

Spatial relationships in major geological events- Recent Events- for spatial setting see maps of areas, look for major tectonic plate boundaries, fault lines.

Events 1996-2001

Other Geologic Hazards- EXAMPLE OF GEOLOGIC ANALYSIS AND GENESIS OF EVENTS TAKING INTO CONSIDERATION ALL FACTORS: Detailed studies include general landscapes (glacial), geological landscapes, mineral resources, spatial setting-site and situation, climate, climate characteristics (summer, fall, winter, spring), climate impacts, climate normals, climate extremes, climate applications, fresh water environment, drainage basins, flood risk zones, cold ocean proximity, marine resource use, biosphere, including ecoregions, forest, wetlands, deserts, lakes, ponds, rivers and streams, postglacial re-colonization nonnative plants and animals and animal extinctions, etc.), geological hazards and disasters, slope instability, like landslides, rockfalls, coastal erosion, coastal flooding, other geological events such as sinkholes, social and economic factors .

 

6. Type of plate boundaries

Plate motions

 

7. Relation of California's Geological Features to Plate Tectonics

The major geologic events in the recent history of California are numerous earthquakes. In earlier history, a major volcanic eruption occurred in the Mono Lake Area out side of Fresno, California. Even earlier were the strong forces that built mountains.

Earthquakes and volcanoes occur at or near major plate boundaries. The San Andreas Fault... a major plate boundary between the Pacific Plate and North American Plates is an example. In addition to major plate boundaries, earthquakes occur along faults. A fault is a crack in the Earth's crust along which movement has occurred.

CLICK on the Four Basic Types of Faults (ANIMATION) to clearly see the difference, then click on each link.. in order.. below.

If you said along fault lines or major plate boundaries (i.e. San Andreas Fault)... you're correct.

Maps of recent earthquake activity in California with fault names (click on map to zoom in on area desired)- REAL TIME DATA... CLICKING ON EARTHQUAKE EPICENTER WILL BRING UP DETAILS)

PREDICTING CALIFORNIA EARTHQUAKES

Hazards and Preparedness

Crustal Deformation and mountain building

Plate tectonics, volcanoes and igneous rock evolution

Recent California Earthquakes and association with faults

 

8. Relation of causes of earthquakes, volcanoes and earth's resources to tectonic forces

Relationship of earthquakes to plate tectonics

Relationship of Volcanoes to plate tectonics- Animation- The pressure and friction from the plate moving under a major plate (subduction zone) cause the solid rock to melt. The great pressure forces the magma (melted rock) to the surface and erupts, spilling out lava (magma on top of the earth) and a new volcano is born (or an old inactive volcano becomes active once again). Mt. St. Helens is an example of a volcano that erupts periodically through time. Click on the word, Plate Tectonics TO BEGIN ANIMATION.

 

 

 

THE ROCK CYCLE illustrated to the left is another cycle powered by the movement of major plates and faults. As described above, solid rock melts beneath the surface of the earth and can cool slowly to form more igneous rock, or recombine the individual elements to form metamorphic rock.

On the surface of the earth, the processes of weathering and erosion form sedimentary rocks.

These rocks contain minerals that ARE VALUABLE RESOURCES FOR USE BY MAN ON EARTH and is the process by which they are generated.

Volcanic eruptions also are a source of these minerals. Depending on the type of eruption that occurs different types of lava (mineral content) are formed.

 

 

 

 

 

Eruptive Style Volcanic Structures (Table below)
Magma
Temperature
Silica content
Style of eruption
Tectonic setting
Rhyolytic
Low
High (> 70%) (lava very thick)
Violent

Oceanic/continental subduction zones (see the animation for divergent boundaries to understand what subduction zones are. )

Oceanic volcano (movie)

Andesitic
Low to moderate
Medium (60%) (lava medium thickness)
Moderate violent to violent
Oceanic/continental subduction zones, volcanic island arcs
Basaltic
High
Low (40-50 %) (fluid lava)
Peaceful

Divergent boundaries (hot spots)

Divergent boundary animation

In new window click on "Plate Tectonics" to see shockwave animation. Illustrates divergent boundaries and subduction zones.

 

Igneous Activity

Plutons

Products of Volcanic Eruptions

Gases (steam can be as high as 90% of all gases produced during eruption)

Lava

That flows easily and quietly with little eruptive violence
Or slowly

 

If large quantities of gas are released at the same time this causes minor explosions hurtling red-hot lava into the air

 

Tephra: Some spew enormous volumes of solids, gases and particles from boulders, fragments of rocks to the finest dust (ash). This is collectively called tephra.

 

Terrestrial Volcanoes (introduction)

The Nature of Volcanoes (terrestrial

Principle types of volcanoes (terrestrial) BE SURE TO CLICK ON PICTURES OF DIFFERENT TYPES AND THEN ON THE JPG FILE TO SEE SPECTACULAR VIEWS OF THE DIFFERENT TYPES OF VOLCANOES.

Volcanoes: Historic Eruptions

Volcanoes that destroy

 

Volcanoes that build

Volcanic Lightning also great picture of lightning produced as a result of eruption
Formation of Hawaiian Islands- Introduction- to focus on each Hawaiian volcano on the map in the new window, click on the red spot.

9. Summarize earthquake processes in terms of epicenter, focal mechanism, distance, and materials, and the role various factors play in the amount of damage caused by an earthquake

Locating Earthquakes The term, epicenter, refers to the area ON TOP of the Earth's surface above the place where the movement of the earth started. In the link they talk about the term hypocenter OR FOCUS. It is the term for the real position within the crust of the earth where the movement of the fault occurred.

Also contains information about damage vs distance from quake. Like light, the energy of a quake decreases more than the inverse of the square of the distance. What this means is that if you are twice as far away from the hypocenter OR FOCUS as your neighbor you will experience less than one-fourth of the energy...hence, less destruction.

The effect of soil type to shaking hazard - San Joaquin Valley was once the bottom of an ancient lake. Due to this and it's soil properties it has the tendency to "shake like jello", absorbing much of the energy from the waves emanating from the hypocenter OR FOCUS.

The greatest damage occurs when S-waves move side to side rather than up and down, or if the movement of a fault produces a Love-wave (side to side).

The Cause of Earthquakes/Volcanoes/Relationship to people

 

10. Types of waves in earthquakes

P and S Wave Animations- Also contains great graphic to understand epicenter, focus (hypocenter) and fault.

Details about P, S, Love and Rayleigh waves - Click on View and Text Size and increase the size of the text to be able to distinguish it from its background.

 

 

2.2 Rock Formation

a. Diagram and explain the rock cycle
b. Describe relative and absolute dating techniques, including how half-lives are used in radiometric dating
c. Describe the law of superposition and relative age dating.
d. Identify evidence, including radioactivity, stratigraphy, fossils, magnetism of rocks, geochemistry, and atmospheric composition, for the age of the earth

e. Identify the broad divisions of geologic time and the major fossil classes of each
f. Compare uniformitarianism and catastrophism
g. Summarize the evidence in rocks and plant fossils for the evolution of the atmosphere

1. Diagram and explain the rock cycle

The Rock Cycle

 

 

2. Describe relative and absolute dating techniques, including how half-lives are used in radiometric dating

Radiometric dating

More on radiometric dating (1 page)

Relative time scale

Absolute dating

3. Describe the law of superposition and relative age dating.

Law of Superposition- Niclaus Steno said the younger the rocks, the higher up they are in rock layers. The older the rocks the lower they are.

Techniques using the law of superposition for relative age dating

 

4. Identify evidence, including radioactivity, stratigraphy, fossils, magnetism of rocks, geochemistry, and atmospheric composition, for the age of the earth

Age of the Earth -Introduction

Scroll down to magnetic stripping and polar reversal - Magnetism of rocks

Geochemistry techniques and age of the earth

Atmospheric composition and the age of the earth

Relative time scale -Stratigraphy including radioactivity and the age of the earth

Fossils and the age of the earth... see below

 

 

5. Identify the broad divisions of geologic time and the major fossil classes of each

Links to the fossil classes according to the Geological time period are found on the chart to the left. The following links are available:

PRECAMBRIAN ERA -Click anywhere in the Precambrian, Protezoic or Archean EON's

 

Representing the Paleozoic era

Cambrian, Ordovician, Silurian, Devonian, Mississippian, Pennsylvanian and Permean- Click on each period individually.

 

MESOZOIC ERA- Click anywhere in the Mesozoic era, Triassic, Jurassic and Cretaceous periods

 

CENOZOIC ERA- Click anywhere in the Cenozoic era, Tertiary, Paleogene, Nenogen or Quaternary periods.

 

 

 

 

6. Compare uniformitarianism and catastrophism

Catastrophism

Uniformitarianism

 

 

7. Summarize the evidence in rocks and plant fossils for the evolution of the atmosphere

Evidence in rocks and plant fossils for the evolution of the atmosphere

 

 

2.3 Shaping Earth's Surface: Surficial Processes and Features

a. Describe the dynamic processes of erosion, deposition, and transport
b. Describe the coastal processes including beach erosion and natural hazards
c. Explain the location of deserts on Earth
d. Describe the significance of geologic structures and rock properties to surficial processes
e. Describe the effects of natural hazards, including earthquakes, volcanic eruptions, landslides, and floods, on natural and human-made habitats and environmental and human responses to those events

 

1. Difference between Weathering and Erosion

Weathering
Mechanical (Physical) Weathering- Heat spalling (The cracking and flaking of particles out of a surface as a result of heat), Joint fracture and frost wedging.
Mechanical/Physical Weathering- Root wedging (plants and trees growing in cracks of rocks...roots increase in size and push rocks apart) and exfoliation (water freezes in surface cracks parallel to surface of rock and pieces fall off).
Chemical Weathering- produced by oxidation, hydrolysis (ion exchange)
Chemical Weathering- example of hydrolysis and oxidation of iron-containing rocks- can also be moss/algae growing and dissolving minerals through acid production.
Chemical Weathering- Climate (maps)

Mechanical weathering aids chemical weathering

 

TABLE: FACTORS INFLUENCING THE SPEED OF CHEMICAL AND

PHYSICAL WEATHERING

Slow weathering
Intermediate Weathering
Fast Weathering
Mineral resistance to chemical weathering
High resistance (e.g. quartz)
Intermediate resistance (e.g. mica and feldspar)
Low resistance (e.g. calcite and olvine)
Frequency of joints
Few joints (meters apart)
Intermediate joints (0.5 to 1 m apart)
Many joints (centimeters apart)
Depth of regolith (The irregular blanket of loose, non-cemented rock particles that cover the Earth.)
Zero
Shallow
Deep
Steepness of slope
Steep
Moderate
Gentle
Vegetation
Sparse
Moderate

Dense

Temperature

and rainfall

Cold (Average 5 degrees C)

Low Rainfall (<10 cm per year)

Intermediate Average (15 degrees C)

Intermediate rainfall (10-130 cm per year

Warm average (about 25 degrees C)

High rainfall (> 130 cm per year

Burrowing animals/insects
Rare
Frequent
Abundant

 

 

Erosion

Streams- water- the most powerful force of erosion

Glaciers- cannot sort particles

Wind- the weakest force of erosion

Waves - waves carve the ocean shoreline

Mass Wasting

Subsidence

Erosion/Weathering combination- Hoodoos

 

2. Shoreline Erosion/Weathering

 

Current, Waves and Tides: Introduction

Click here to access Physical OCEANOGRAPHY

 

 

3. Location of Deserts on the Earth (explanation)

Summary of location of deserts on the Earth

More Details: Deserts on the Earth

 

 

4. Describe the significance of geologic structures and rock properties to surficial processes
INTRODUCTION TO MATTER AND MINERALS: From the University of Texas at Arlington

MATTER
Matter is anything that has mass and volume. Matter can be subdivided into two groups on a chemical basis:
  • substances composed of elements and compounds, and
  • mixtures which are aggregates of elements and compounds.

 

SUBSTANCES
  • Elements
Chemists and physicists have identified 112 basic substances. Ninety-two such substances are known to occur naturally in earth's crust. These substances are referred to as elements because each consists of an atom having a nuclear charge which does not vary, and because none can be separated into different particles except by nuclear disintegration. Some of the more common elements in the earth are:

Element Symbol

Element Name

Weight Percent

0

Oxygen

46.60

Si

Silicon

27.72

Al

Aluminum

8.13

Fe

Iron

5.00

Ca

Calcium

3.63

Na

Sodium

2.83

K

Potassium

2.59

Mg

Magnesium

2.09

TOTAL

98.59


 

  • Compounds

    The study of matter was greatly simplified when it was demonstrated that the seemingly endless variety of substances found within the lithosphere, hydrosphere, biosphere, and atmosphere of earth are derived from only a fraction of the 112 elements. These substances result from the natural combination of a number of elements in various proportions to form chemical compounds. Water, the most abundant substance on the surface of the earth, is a compound formed by the combination of the elements hydrogen and oxygen. Water can be decomposed to atoms of hydrogen and oxygen by a process known as hydrolysis (the passing of an electric current through water).

    A compound always contains its constituent elements in the same proportion. Water, with the chemical formula H2O, is composed of two atoms of hydrogen (H2) and one atom of oxygen (O). This ratio of two parts hydrogen to one part oxygen is constant for water. If the ratio changes, then the compound ceases to be water and becomes another compound identified by its chemical formula. This is so because the smallest particle of water that has the properties of water, the water molecule, consists of two atoms of hydrogen bounded with one atom of oxygen. Regardless of the volume of water, the proportion of hydrogen to oxygen is a fixed constant.

    Compounds rarely have the appearance of the elements from which they are composed. The mineral halite with the chemical formula, NaCl, is a compound formed by linking or bonding one atom of sodium (Na) to one atom of chlorine (Cl). Separately, neither element is suitable for consumption; sodium is a metal that burns readily when brought into contact with water, and chlorine is a highly toxic gas. When combined however, they form the compound halite (NaCl) or common table salt. The lack of correspondence between the appearance of compounds and their constituent elements presents difficulties in understanding the nature and variety of compounds and materials common at earth's surface.

     

MIXTURES

Most natural things we come in contact with are mixtures rather than single elements or even single compounds. Mixtures are not pure substances but are aggregates of elements and compounds which retain their own identity when blended. That is, the molecules of the compounds do not react to form different molecules. For example, when halite (NaCl) is placed in water, the water molecules dissolve the salt crystals and decompose most halite molecules to sodium and chlorine atoms even though some halite molecules retain their basic identity of NaCl. This is typical of sea water which is a mixture composed of water, elements, and compounds. The proportion of the constituents of a mixture can vary while those of compounds cannot. For sea water, a salinity of 35 parts per thousand (ppt) indicates that each liter (1,000 milliliters) of the sea water contains 965 parts water (H2O) and 35 parts of other compounds and elements. Mixtures with the same constituents, but with salinities ranging from 25 to 100 parts per thousand would also be classified as being sea water.

 

PROPERTIES OF MINERALS

Most of what we now know or will know of earth history is contained in rocks. All rocks are composed of minerals or fragments of other rocks which are themselves composed of minerals. Rocks may consist of one mineral (the mineral halite also forms a rock known commonly as rock salt) or more than one mineral or rock fragments of other rocks. Minerals are the key to interpretation of earth history because each mineral formed under a set of circumstances which provide knowledge of a segment of earth history during the crystallization of that particular mineral. Such interpretation is possible because the physical circumstances which combined to allow the mineral to form has not changed with geologic time. That is, the rock limestone formed of mostly the mineral calcite has had the same mode of formation for all of earth history. Environments in which minerals form range from that in which we live to those deep within earth's crust. In order to understand earth history, it is therefore necessary to correctly interpret this information. Rocks of this type are then either compounds or mixtures. The first step toward understanding the geologic message contained within rocks is understanding the history of the formation of the component or components of the rock, i.e., the minerals or rock fragments.

 

DEFINITION OF A MINERAL
A substance or a mixture is a mineral when it has the following properties.
  1. Occurs as a natural inorganic solid.
  2. Has a specific internal structure resulting from the definite arrangement of its own constituent atoms into a crystalline solid.
  3. Has a chemical composition that varies within defined limits and that can be expressed by a chemical formula.
  4. Recognizable by certain physical properties that reflect the combination of chemical composition and atomic structure.

Chemical analyses of rock reveal that approximately 99% of the materials of earth's crust are composed of only 8 elements, and that two of these elements, silicon (Si) and oxygen (O), comprise almost 75% of these materials. The 8 most common elements are listed in the table below in order of their abundance. The majority of minerals can be considered as combinations of only these 8 elements, a fact that greatly simplifies the study of earth materials. The remaining 84 naturally occurring elements account for only slightly more than 1 % of the earth's crust and can be ignored for the purposes of this course.

 

RELATIVE ABUNDANCE IN WEIGHT PERCENT OF THE

EIGHT MOST ABUNDANT ELEMENTS IN EARTH'S CRUST

Element Symbol

Element Name

Weight Percent

0

Oxygen

46.60

Si

Silicon

27.72

Al

Aluminum

8.13

Fe

Iron

5.00

Ca

Calcium

3.63

Na

Sodium

2.83

K

Potassium

2.59

Mg

Magnesium

2.09

TOTAL

98.59

 

 

 

 

 

 

 

Silicate Minerals

Non-Silicate Minerals

Identifying the physical properties of minerals

CLICK HERE TO SEE PICTURES AND PROPERTIES OF ALL MINERALS

Igneous rock distribution and plate tectonics (Be sure to click on all links in this page)

Introduction to Sedimentary Rocks (Be sure to click on all links in this page)

Metamorphic rock classification (Be sure to click on all links in this page)

 

 

5. Describe the effects of natural hazards, including earthquakes, volcanic eruptions, landslides, and floods, on natural and human-made habitats and environmental and human responses to those events

Groundwater and the Hydrologic Cycle- Groundwater takes you to an index page. Total document is 20 pages; Hydrologic Cycle takes you to a single page review. Click here for a more detailed account of the water cycle

       

Recharge of Groundwater -University of Alabama

        Groundwater is recharged from precipitation falling on aquifer rock outcrops or by precipitation infiltrating through the zone of aeration. Factors controlling natural recharge:

  1. Amount of moisture used by vegetation.
  2. Nature of precipitation event.
  3. Presence of any subsurface barriers to now.
  4. Amount of groundwater used by humans.

In some areas, natural recharge is less than groundwater withdrawal and aquifers may have to be artificially recharged by the re-injection of water into wells or the use of recharge basins.

 

Groundwater Erosion and Deposition

        Chemical weathering causes dissolution of carbonate rock (limestone and dolostone) in contact with groundwater containing carbonic acid (produced from carbon dioxide in the air and from organic decay). Chemical weathering by groundwater produces several features in areas with carbonate bedrock:

  • Caves and Cave Deposits form at or below the water table in limestone and dolostone through dissolution. Caves can be brought above water table by uplift and/or erosion. More than 17,000 caves are known in the US.
    • Caves are a naturally formed subsurface opening that is generally connected to the surface and is large enough for a person to enter. A cavern is a very large cave or system of interconnected caves.
    • Cave deposits or dripstones are deposits of calcium carbonate that form as groundwater evaporates in caves. Kinds of dripstone formations include:
      1. Stalactites - hang down from ceiling of cave.
      2. Stalagmites - grow upward from floor of cave.
      3. Columns - form when a stalactite and stalagmite meet.
      4. Drip curtains - vertical sheets of dripstone formed by water seeping through crack in cave ceiling.
      5. Travertine terraces - layers of dripstone formed by water flowing across the floor of a cave.

       

  • Karst topography represents landscapes shaped by the dissolution of underlying limestone or dolomite by groundwater. Karst forms in humid and temperate climates. Caves and springs are common, and other features include:
    1. Sinkholes form by the collapse of an underground cavity or by dissolution of soluble rock below a soil layer. Sinkholes can fill with water to form a lake.
    2. Solution valleys are caused by the coalescence of sinkholes, and locally contain disappearing streams (stream flows into a sinkhole).
Problems Caused by Human Modifications of Groundwater System

        Groundwater currently provides about 20% of all water used in the US. Human modification of the groundwater system can have several long-lasting consequences:

  • Lowering of the water table occurs where groundwater is withdrawn faster than it can be recharged. It can cause wells to dry up; for example: in some areas of the Midwest, 2-10x more water is being withdrawn from the High Plains aquifer than is being recharged.
  • Saltwater incursion involves contamination of freshwater aquifers with saltwater. Fresh water floats as a lens on denser salt water. If too much fresh water is removed, a cone of depression is created in the fresh water lens. Lowering the water table by 1 foot results in raising the level of salt water by 40 feet. This situation occurs primarily in island or coastal communities, but is also threatening the Salinas Valley in California. It can be counteracted by:
    1. Reducing groundwater withdrawal.
    2. Re-injecting treated wastewater into recharge wells.
    3. Construction of recharge ponds.
  • Land subsidence occurs where excessive pumping of groundwater removes ground support, particularly in areas of unconsolidated sediments and sedimentary rocks. Removal of water causes sediment compaction. The weight of buildings can also cause compaction and subsidence.
  • Pollution - Sewage is the most common source of groundwater pollution. Landfills, underground storage tanks, and hazardous waste disposal sites are other sources of contamination. Surface sources of pollution can affect groundwater where the ground is very permeable or where conduits to the water table are present. Pollution spreads with the flow of groundwater. Cleanup of contaminated groundwater is extremely difficult and expensive. High-level nuclear waste disposal may threaten groundwater quality in the future.
Hot Springs and Geysers

        These features are produced by groundwater percolating into areas heated by igneous activity or by deeply circulating water heated by the geothermal gradient.

  1. Hot springs are springs that bring water to the surface that is at least 6.5 degrees C higher than the mean air temperature. Most US hot springs are located in the West, and are produced by igneous activity.
  2. Geysers are hot springs which periodically emit columns of water and steam with great force. They occur where groundwater percolates into underground chambers that exist in hot rock. Water eventually boils under great pressure and forces its way to the surface. Cooler groundwater seeps back in, and the cycle is repeated.
Geothermal Energy

        This is energy produced from steam and hot water trapped in the Earth's crust. Relatively nonpolluting power sources, geothermal areas are often protected, typically remote from population centers, and have a limited lifetime.

Chemical and Physical Factors: Influence of processes on ecosystems

 

 

 

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