Notes, summaries, assignments, exams, and problems for Geology

Earth's Internal Structure and Plate Tectonics

Seismic Wave Behavior at Different Depths

P-waves (primary waves) and S-waves (secondary waves) are seismic waves that travel through the Earth's interior. At a depth of 100 km, P-waves have a speed of 6 km/s. This speed increases to 8 km/s as the material becomes more rigid. The speed then decreases at the Mohorovičić discontinuity. After 300 km, the speed begins to rise again until it reaches a point where it increases slowly because the material is less rigid. The Repetti discontinuity separates the lower mantle from the upper mantle. Continuing on, P-waves reach a point where their speed plunges at a depth of over 3,000 km. This is where S-waves diminish completely, as the material is more... Continue reading "Earth's Layers, Seismic Waves, and the Wilson Cycle" »

Earth's Internal Heat and Convection Movements

The heat accumulated inside the Earth causes convection movements.

Density relates to temperature: heat reduces density; heat and density vary quantitatively.

Fractures and Diaclases

Diaclases are brittle deformations or cracks in materials, with dimensions on the order of millimeters.

Faults and Block Displacement

Faults are deformations of brittle materials where blocks are displaced. Fault types include the following:

Hanging Wall and Fault Motion

In reverse (inverse) faults, the hanging wall moves upward relative to the footwall and is tilted toward the uplifted block. In normal faults, the hanging wall moves downward relative to the footwall.

Convection Currents in Fluids

Movements consist of convection... Continue reading "Mantle Convection, Faults, Volcanism and Earth's Dynamics" »

Chapter 6 - Glaciers

Glacier Formation

Describe how glaciers form (using the terms zone of accumulation and zone of ablation).

Zone of Accumulation

• The area where a glacier forms.
• More snow falls in winter than melts in summer.

Zone of Wastage

• The area where there is a net loss due to melting.

Zone of Fracture

• Uppermost 50 meters.
• Crevasses form in brittle ice in this zone.

What part of the glacier behaves brittly? Plastically?

Types of Glacial Movements

• Plastic flow
• Slipping along the ground below 50 meters

Brittly in the picture

Valley Glaciers vs. Continental Glaciers

What are valley glaciers? Continental glaciers? Examples of each.

1. Valley, or alpine glaciers – form in mountainous areas
2. Ice sheets, or continental glaciers
   • Large scale e.g., Over Greenland

Chapter 8 – Earthquakes

What is the elastic rebound theory? Is it possible for energy building up in the lithosphere to be released in a sequence of earthquakes?

Rocks “spring back” – a phenomenon called elastic rebound

Energy is released in a sequence of earthquakes (one earthquake can trigger slip on a nearby fault)

What is a seismic body wave, and what characterizes each of the two types of body waves (i.e. type of motion, velocity)?

1. Primary(P) waves(spring)=push&pull motion, greatest velocity, arrive first, travel solid, liquid, gases.
2. Secondary(S) waves (rope)=up&down motion, slower velocity, arrive after P at seismograph, travel only solid.

What is a seismic surface wave, and what characterizes each of the two types of surface

Adipocere Formation Over Time

On Earth, over time, adipocere undergoes certain changes that allow us to distinguish between recent (or young) adipocere and old adipocere. Recent adipocere may show little uniformity and thickness on portions of foreign tissues (remains of muscles, tendons, or ligaments). Old adipocere is hard, dry, and somewhat brittle; its structure is more homogeneous.

Conditions for Saponification

Environmental Conditions

Circumstances that favor adipocere formation include:

1. When the corpse has been submerged in water or in an area of low current.
2. When the corpse has been buried in damp clay soil.
3. When many bodies have been buried in contact with each other: the bodies in the lower layers tend to saponify to a greater or lesser

1 - The Deciduous Forest

It consists of tall trees with straight trunks, smooth bark, and large leaves that fall in autumn. This forest type has relatively few species, often forming large masses. The most common features are Carballo oak and beech. In the understory, ferns and mosses thrive in a somber mood created by the treetops.

2 - The Heath and Grasslands

The Landa is a dense shrubland, whose height can be low or reach 4 feet. Its most abundant species are heather, gorse, and broom. The heath is considered a form of deciduous forest degradation or supraforestal vegetation. It is often used for animal bedding and then as fertilizer.

The meadows are herbaceous vegetation occupying large tracts of land with ocean views.

The Vegetation of the

Plate Tectonics: Key Concepts

• Biological Puzzles

  The existence of land bridges or island chains that connected the ancient continents.

• Geographic Enigmas

  The outer edge of the continent is under the sea where the continental shelf terminates.

• Geological Riddles

  There is a correspondence between geological structures present on both sides of the Atlantic Ocean.

Scenarios of Continental Drift

According to Wegener, all continents were part of a large landmass (supercontinent called Pangea).

• Paleomagnetic Tests

  During the cooling of lava, ferrous minerals align. Studying these minerals indicates the position of the north pole.

• Oceanographic Evidence

  The discovery of the oceanic ridge system that splits the great oceans.

• Seafloor Spreading Hypothesis

  Harry Hess

Chapter 5 - River Systems

How rivers and streams work – Gradient (know this!)

• Streamflow
  • Factors that determine velocity
  • Gradient, or slope
  • Channel characteristics
    • Shape
    • Size
    • Roughness
    • Discharge – volume of water flowing in the stream (generally expressed as cubic feet per second)
• Gradient highest nearest river source, where is it lowest?
• Upstream-downstream changes
  • Profile
  • Cross-sectional view of a stream
  • From head (source) to mouth
  • Profile is a smooth curve
  • Gradient decreases from the head to the mouth
  • Factors that increase downstream
    • Velocity
    • Discharge

Base level

Rivers flow and/or erode to the lowest level, ultimately to sea level

• Base level
  • Lowest point a stream can erode to
  • Two general types
    • Ultimate – sea level
    • Temporary, or local
  • Changing causes readjustment

Atmospheric Layers and Structure

The Troposphere

The troposphere concentrates the bulk of the atmosphere's mass and all moisture and dust particles. It extends up to 16 km in Ecuador and a minimum of 8 km at the poles. It is where all weather phenomena, such as wind and rain, develop.

The Ionosphere

Situated between 90 and 400 km, the ionosphere is ionized and reflects radio waves.

Environmental Impact Assessment

Declaration of Environmental Impact (EID)

Communication is required by law regarding predicted environmental consequences, and should include the following:

• Project description.
• Consideration of alternatives to actions that are performed.
• Environmental inventory prior to completion of the activity.
• Identification of anticipated impacts.
• Protective

Understanding Natural Resources

In human terms, a resource is anything we obtain from the environment to satisfy our needs and desires. All living things require basic resources such as food, water, and shelter. Some resources are directly usable, while others require effort or technology to become useful.

Types of Natural Resources

Perpetual Resources

These resources are virtually inexhaustible on human timescales. Examples include direct and indirect solar energy (wind, running water).

Non-Renewable Resources

Non-renewable resources exist in a fixed amount within the Earth's crust. They may form through natural processes, but over millions or billions of years (e.g., oil takes 600 million years to form). While complete exhaustion is rare, economic... Continue reading "Understanding Natural Resources: Types, Sustainability, and Challenges" »