Cosmology
Describe the difference between geocentric and heliocentric.
The geocentric model states that Earth is the center of the Solar System and the Sun along with the other planet orbit around Earth.
The heliocentric model states that the Sun is the center of the Solar System and Earth one of the planets surrounding it.
What are the 5 layers of Earth and describe their characteristics. (Composition, how they behave)
Crust - Primarily SILICATES (silicon and oxygen) with abundant aluminum.
1. Lithosphere: Solid, strong outer layer crust + uppermost mantle. Behaves as brittle shell.
Mantle - Primarily SILICATES (silicon and oxygen) with abundant magnesium.
2. Asthenosphere: Weak, partially molten. Deforms plastically. Low-velocity zone.
3. Mesosphere: Lower mantle, not as ductile.
Core -
4. Outer Core: Liquid, primarily iron and nickel with sulfur and oxygen.
5. Inner Core: Solid, primarily iron and nickel.
Describe the 3 types of plate boundaries and their characteristics.
Transform - Plates move past each other, extreme earthquake hazard, volcanos are absent.
Convergent - Plates collide together, subduction zones, extreme earthquake and volcanic hazard, area of low topo (basins/trenches) next to area of high topo (mountains/volcanos).
Divergent - Plates pull apart from each other, continental rifting (EQ + volcanos), seafloor spreading (some EQ + volcanos).
Define deformation and the 2 different types, along with the mechanisms that control them.
Deformation refers to a change in location, orientation, shape or volume due to applied stresses coming from tectonic movement.
1. Brittle - material breaks (discontinuous) FAULTING (low T, low to moderate P)
2. Ductile - material flows without breaking (continuous) FOLDING (high T, high P)
Mechanisms (depending on):
1. Temperature
2. Pressure
3. Deformation rate
4. Composition
What is an earthquake? Where do most earthquakes occur? What plate boundaries have the largest and most frequent earthquakes?
Earthquake: When the stress reaches a critical level (rock strength + friction) the rock fails and breaks along a new or pre-existing fault generating an earthquake (movement). The accumulated energy is released when the fault ruptures as seismic waves (vibrations).
Most earthquakes occur along the boundaries of tectonic plates, where the Earth's lithosphere is under stress due to the movement of these plates.
1. Subduction Zones (Convergent Boundaries): Subduction zones are locations where one tectonic plate is forced beneath another plate into the Earth's mantle. These zones are associated with the largest and most powerful earthquakes on Earth, often reaching magnitudes greater than 9.0.
2. Transform Faults (Transform Boundaries): Transform faults are fractures where tectonic plates slide past each other horizontally. Although they may not produce the largest earthquakes, transform faults are associated with frequent seismic activity due to the buildup and release of stress along the fault lines. (San Andreas Fault)
What is the Goldilocks effect
The Goldilocks effect refers to a situation where something is optimal or just right not too much, not too little, but perfectly balanced. Earth is not too cold and not too hot. The CO2 concentration of Earth is also just right. Temperature, composition and atmosphere conditions favor life, and it is dynamic and ever-changing.
Describe the 2 types of crust. (Composition, how they behave)
Oceanic crust - Dense, thin, mafic (gabbro and basalt), low SiO2 (magnesium + ferric)
Continental crust - Less dense, thick, felsic (varying composition but primarily rhyolite and granite), high SiO2 (quartz + feldspar)
What are the subdivisions of each plate boundary?
(Hint: Convergent - 3 types)
Convergent: Oceanic-Continental, Oceanic-Oceanic, Continental-Continental
Divergent: Continental-Continental, Oceanic-Oceanic
Transform: Oceanic-Oceanic, Continental-Continental
What types of stresses and structures form at the different plate boundaries?
Divergent: Tensional stress - Normal Faults, Mid-Ocean ridges, Rift Valleys
Convergent: Compressional stress - Reverse + Thrust Faults, Volcanic Arcs, Fold Mountains, Deep Ocean Trenches
Transform: Strike Slip Faults (Right + Left Lateral), Fracture Zones, Offset Landforms
Explain what the hypocenter/focus and epicenter are.
When the accumulated strain energy exceeds the strength of the rocks, it is released suddenly in the form of seismic waves, resulting in an earthquake. The point within the Earth where the energy is released is called the focus or hypocenter, while the point on the Earth's surface directly above the focus is called the epicenter.
Describe the characteristics of the inner and outer planets.
Explain the role density plays within the Earth's crust.
Denser material will "sink", less dense material will "float". This interaction is seen within subduction zones for example. The oceanic crust subducts ("sinks") below the continental crust as they merge together because the oceanic crust is denser than the continental crust.
Describe the force(s) that control plate motion.
Mantle Convection: The mantle beneath the Earth's lithosphere is in a constant state of convective motion. Heat from the Earth's core drives convection currents in the semi-fluid mantle material. As hot mantle material rises towards the surface, it spreads out laterally beneath the lithospheric plates. This motion pushes the plates apart at divergent boundaries. Cooler, denser mantle material sinks back down into the mantle at subduction zones, pulling the plates along with it and driving plate motion at convergent boundaries.
Slab pull and Ridge push: Slab pull refers to the gravitational force exerted on a subducting tectonic plate as it sinks into the mantle at a subduction zone. The weight of the dense oceanic lithosphere pulls the rest of the plate down into the mantle. Ridge push occurs at mid-ocean ridges where new oceanic crust is formed through volcanic activity. The elevated ridge pushes the lithospheric plates away from the ridge axis due to the force of gravity.
Define the Principles of Horizontality, Superposition and Uniformitarianism.
Principle of Original Horizontality: sediments deposited in layers parallel or subparallel to the Earth's surface.
Principle of Superposition: in a layered sequence of rock, each layer is younger than the one below it and older than the one above it.
Uniformitarianism: a geological principle that suggests that the same natural processes and laws that operate in the universe now have always operated in the past and will continue to operate in the future. "The present is the key to the past."
Describe the different seismic waves. Which waves are the fastest? Which waves cause the most damage? What is the particle motion of each?
Body Waves (P+S waves): Move WITHIN the Earth (faster).
Primary Waves (P-waves):
Secondary Waves (S-waves):
Surface Waves:
Explain the Nebular theory.
The nebular theory proposes that the solar system formed from a giant rotating cloud of gas and dust called a nebula. As the nebula collapsed due to gravity, it began to spin faster, forming a flattened disk shape. Within this disk, matter began to clump together to form protoplanetary disks, which eventually developed into planets, moons, asteroids, and other celestial bodies. The central mass that formed became the Sun.
How do we know the Earth is layered? How are the boundaries defined?
We know that the Earth is layered primarily through the study of seismic waves and their behavior as they pass through the Earth's interior. Seismic waves are generated by earthquakes or other sources and travel through the Earth, interacting with different materials and structures along the way. The behavior of these waves allows scientists to infer the internal structure of the Earth. The boundaries between the Earth's layers are defined based on changes in the properties of materials, such as density, composition, and physical state (solid, liquid, or semi-fluid).
What were the key components of Harry Hess's theory of seafloor spreading, and how did it contribute to our understanding of plate tectonics?
Henry Hess's explanation of seafloor spreading suggests that new oceanic crust is formed at mid-ocean ridges through volcanic activity and then moves away from the ridge axis (young crust @ MOR, old crust away from MOR). This drives the movement of tectonic plates. Hess also explains that along subduction zones, old oceanic crust sinks under continents into mantle in deep-sea trenches and the continents are "along for the ride".
What is the difference between an anticline and a syncline, and how do you recognize these folds?
Anticline: upfold that contains older rocks in its core. "Arch"
Syncline: downfold that contains younger rocks in its core. "Trough"
Anticlines & synclines often occur in sets. The resulting compression force causes the alternations between anticlines & synclines. This is a basis to mountain building.
Explain how earthquakes occur in terms of stress.
Compression: Compression stress occurs when tectonic plates collide or converge against each other. This type of stress pushes rocks together, causing them to deform and accumulate strain energy.
Tension: Tension stress occurs when tectonic plates move away from each other, creating extensional forces that stretch and pull rocks apart. This stress can lead to the formation of faults and fractures in the crust.
Shear: Shear stress occurs when tectonic plates slide past each other horizontally in opposite directions. This type of stress causes rocks to move sideways along faults, accumulating strain energy as they resist movement.
How did the moon form?
At 4.5 billion years ago (in just a few hours) a Mars-sized planetesimal collides with proto-Earth. The core of impactor segregates and joins Earth’s. Lighter crust of both bodies melts, forming magma ocean. Large raft of debris is ejected to space. Impact knocks Earth off-kilter by 23˚, speeds rotation. Debris aggregates to form proto-Moon.
Explain how Earths magnetism works. What are the causes and effects of this?
Earth's magnetism comes from the movement of molten iron and nickel in the outer core. This movement generates electric currents, which in turn creates a magnetic field around the planet.
Causes -
1. Geodynamo Process: The primary cause of Earth's magnetism is the geodynamo process. It involves the movement of conductive materials (molten iron and nickel) in the outer core of the Earth. This movement generates electric currents due to the Coriolis force and thermal convection.
2. Rotation of the Earth: Earth's rotation contributes to the generation of its magnetic field. The rotation of the planet induces motion in the conducting materials in the outer core.
Effects -
1. Magnetic polarity reversals along MORs: Earth's magnetic field periodically undergoes reversals, where the magnetic north and south poles switch places. These reversals are recorded in rocks as changes in the orientation of magnetic minerals. During periods of normal polarity, magnetic minerals align with the current magnetic field, pointing towards the present-day magnetic north pole. During periods of reversed polarity, magnetic minerals align in the opposite direction, pointing towards the present-day magnetic south pole. At mid-ocean ridges, new oceanic crust is formed through volcanic activity. Magma rises from the mantle to create new crust, which then spreads away from the ridge axis on both sides. As new crust forms, it records the magnetic polarity of Earth's magnetic field at that time. This process leads to the formation of symmetrical bands of magnetic polarity along the mid-ocean ridge, with alternating stripes of normal and reversed polarity.
What evidence did Alfred Wegener present to support his theory of continental drift?
1. Fit of Continents: Wegener noticed that the coastlines of South America and Africa appeared to fit together like puzzle pieces. He suggested that these continents were once joined together and had since drifted apart.
2. Fossil Distribution: Similar fossils of plants and animals were found on continents that are now separated by oceans. Wegener proposed that these organisms could not have crossed vast oceans but instead lived on a single, continuous landmass.
3. Rock Types and Structures: Geological formations, such as mountain ranges and rock layers, showed similarities across continents that are now separated. Wegener argued that these similarities suggested that these landmasses were once connected.
4. Paleoclimatic Evidence: Wegener studied evidence of past climates, such as glacial deposits and coal beds, found in regions that are now located near the equator. He argued that these features could only have formed in regions closer to the poles, indicating that the continents had shifted position over time.
State and describe the different parts of a fold.
(Hint: there is 3)
Hinge Line: Portion of maximum curvature on a fold.
Axial Plane: Imaginary surface defined by connecting hinges of successively nested folds.
Limbs: Less curved "sides" of a fold.
Earthquakes can be described by either intensity or magnitude, define the different earthquake scales.
Intensity Scales:
Magnitude Scales: