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

Isostasy: Lithosphere–Asthenosphere Equilibrium

Isostasy: The equilibrium between the lithosphere and the underlying asthenosphere.

Studying the Ocean Floor

Studying the ocean floor

Echo sounders produce sound waves that travel outward in all directions. The sound waves bounce off the nearest object and then return to the ship. Scientists know the speed of sound in seawater; they can then calculate the distance to the object that the sound wave hit.

Marine Sediment and Pillow Lavas

Marine sediment: very thin. Pillow lavas: volcanic rocks, very young compared with continental rocks.

Antarctic Ocean Floor Features

• Continental shelf: the edge of the continent that lies underwater.
• Continental slope: the area between the continental shelf and the abyssal

Types of Plate Boundaries

1) Constructive or Divergent

Two plates are moving apart from each other. New magma rises to the surface to fill the gap and cools to form basalt. Lava forms volcanoes and rift valleys.

2) Destructive or Convergent

Two plates are moving towards each other. Usually, an oceanic plate sinks below the other and it is destroyed in the subduction zone. Sediments on the sea bed between the two plates are compressed and folded to form the world’s highest mountain ranges.

The friction from the plate movement makes the rocks melt, and this produces volcanoes. Earthquakes are frequent since the ground shakes from the forced movement of rock.

3) Conservative

Two plates move against each other. This may be in the same direction but... Continue reading "Plate Boundaries, Volcanoes, and Earthquake Impacts" »

Composition of Earth's Atmosphere

• Nitrogen (78%)
• Oxygen (20%)
• Argon (1%)

Greenhouse Gases

Examples: H2O, CO2, CH4, NO2, O3

Importance: Without greenhouse gases, Earth's temperature would be -22 to -36 degrees Celsius.

Greenhouse Effect

Solar energy absorbed by Earth and re-radiated as heat by greenhouse gases.

1. Natural Greenhouse Effect
2. Human-Induced Greenhouse Effect (Global Warming)

Global Warming / Climate Change

Caused by burning fossil fuels, deforestation, and human activities that increase carbon dioxide levels, leading to Earth's warming.

Ozone, Hole in Ozone, UV Rays, CFCs

Ozone

Located mostly in the lower stratosphere, it acts as a shield against harmful UV radiation from the sun.

Hole in the Ozone Layer

Causes: Primarily caused by human-made chemicals... Continue reading "Understanding Earth's Atmosphere and Climate Change" »

Hydrocarbon Traps and Petroleum Accumulation

Hydrocarbon traps are any combination of physical factors that promote the accumulation and retention of petroleum in one location. Traps can be structural, stratigraphic, or a combination of the two.

Geologic processes such as faulting, folding, and deposition and erosion create irregularities in the subsurface strata which may cause oil and gas to be retained in a porous formation, thereby creating a petroleum reservoir. The rocks that form the barrier, or trap, are referred to as cap rocks.

Structural Traps

Structural traps are created by the deformation of rock strata within the earth’s crust and are formed by tectonic deformation. This deformation can be caused by horizontal compression or tension,... Continue reading "Mechanisms of Petroleum Accumulation in Geological Traps" »

Coastal Erosion

Factors Influencing Wave Size and Energy

The size and energy of a wave are influenced by:

• How long the wind has been blowing
• The strength of the wind
• The fetch (the distance the wind blows over the surface of the water)

Rate of Coastline Erosion

The rate of coastline erosion is influenced by:

• Type of rock (e.g., chalk and limestone form steep cliffs)
• Strength of waves
• Speed of waves

Destructive Waves

Destructive waves are created in storm conditions. They are characterized by:

• Being created from big, strong waves when the wind is powerful and has been blowing for a long time
• Occurring when wave energy is high and the wave has traveled over a long fetch
• Eroding the coast
• Having a stronger backwash than swash
• Having a short wavelength and being

Volcanoes

Scenario: Consider a geographic location for a volcano. What type of plate setting is it located in? What kind of volcano is it (composite, dome, or shield)? What kind of lava does it produce (rhyolite, andesite, or basalt)? Is the lava predominantly silicate, feldspar, or ferromagnesian? Why? Is the lava felsic, mafic, or a combination in origin? Why? Describe the characteristics of a volcanic eruption.

Plate Tectonics:

• Divergent (mid-ocean ridges = volcanoes)
• Rift zones = volcanoes
• Subduction zones = volcanoes
• Hot spots = volcanoes

Lava

Composition:

• Result of the geologic setting, which determines available source material.
• Extent of melting, which determines what becomes the source material.
• A mix of SiO4, Al, Fe, Mg.

• Rich in SiO4: more felsic

Climate Feedbacks and Their Impact on Climate Change

Feedbacks within the climate system amplify climate changes initially caused by external factors. This can be visualized as:

• Initial climate forcing → Initial climate response → Response amplified

Example: An increase in heat energy sent to Earth by the Sun causes high-latitude snow and ice to retreat. This allows more sunlight to be absorbed by the Earth's surface, leading to further climatic warming (amplifying the changes underway). Another example is delayed bedrock rebound.

Negative Feedback Mechanisms in Climate Change

Initial climate changes can also lead to a reduced response:

• Initial climate forcing → Initial climate response → Response reduced

Example: Chemical weathering acts... Continue reading "Climate Change: Feedbacks, Processes, and History" »

Key Definitions in Hydrology and River Systems

River Features and Drainage Systems

River Channel: The bed and sides of a river form the river channel.

Drainage Basin: The area of land drained by a river.

Confluence: The point where a river and a tributary meet.

Tributary: A smaller river which joins a larger river.

Source: The starting point of a river.

Mouth: The end point of a river, where it enters the sea or a lake.

Watershed: A ridge of highland which determines to which drainage basin the water flows.

The Hydrological Cycle (Water Cycle Processes)

Hydrological Cycle: The continuous movement of water on, above, and below the surface of the Earth (the water cycle).

Evaporation: The change in state from a liquid (such as water) to a gas (such as water... Continue reading "Essential Hydrology and River System Terminology" »

Formation and Evolution of the Universe

The timeline of the universe's formation is marked by several key milestones:

• 10^-32 seconds: Inflation ends.
• 10^-6 seconds: Protons are formed.
• 100 seconds: Elements are synthesized.
• 100 million years: The first star appears.
• 500 million years: Galaxies begin to form.
• 4 billion years: Planets are established.

Types of Cosmological Calculations

Scientists determine these timelines using various calculations, including:

• The rate of expansion calculated back from the beginning.
• The rate of development for different types of stars.
• The rate of formation for known elements.

Friedrich Nietzsche posited that the universe is still expanding and contracting. Regarding stellar lifespans, the typical life of a star is approximately... Continue reading "Universe Evolution and Global Population Dynamics" »