Describe the concept how the Geologic Time Scale was established.
The establishment of the geologic time scale involved the meticulous integration of various principles and observations in the field of geology. Key among these were the Law of Superposition and the Principle of Fossil Succession. The Law of Superposition, formulated by Nicolaus Steno, guided the understanding that, in undisturbed sedimentary rock layers, the youngest rocks are positioned at the top, while the oldest lie at the bottom. This principle provided a relative chronological framework. Complementing this, the Principle of Fossil Succession highlighted the consistent order in which fossils succeeded one another in rock layers, indicating distinct periods of life forms throughout Earth’s history. By examining these fossil assemblages, scientists could correlate and date rock formations. The synthesis of these principles, alongside advancements in radiometric dating methods, allowed geologists to construct a comprehensive geologic time scale, dividing Earth’s history into eons, eras, periods, and epochs, providing a chronological narrative of our planet’s evolutionary journey.
Illustrate the schematic drawing of the hydrologic cycle.
Illustrate the Rock Cycle and briefly describe it.
Illustrate the detailed Layers of Earth based on chemical and physical composition.
Create a comparison table between continental and oceanic crust based on their composition, density, thickness, elevation, and age.
Illustrate the Major layers and seismic (P - wave) velocity changes within Earth, with details of the
upper mantle layers.
Can you provide details on the composition of Earth’s core, including the primary elements and the discontinuity observed at 2900 km, leading to the inference of a liquid outer core? Additionally, explain the role of circulating molten iron in the outer core in generating Earth’s magnetic field.
The Earth’s core is primarily composed of iron (approximately 85%), with significant amounts of nickel (about 5%) and lighter elements (around 8-10%), such as oxygen, sulfur, and/or hydrogen. A significant change in seismic wave velocities occurs at the 2900 km discontinuity, known as the Gutenberg discontinuity or core-mantle boundary. This change indicates the outer core is inferred to be a liquid, as S-waves are not transmitted through non-rigid substances like fluids.
Geophysical studies suggest the Earth’s outer core is a highly compressed liquid with a density of approximately 10-12 g/cm³. The circulation of molten iron in the outer core is crucial for generating Earth’s magnetic field.
Can you provide a straightforward explanation of the phenomenon happenning at Lehman discontinuity? Additionally, describe the characteristics of Earth’s inner core based on its density, composition, and seismic property.
The outer/inner core boundary, the Lehman discontinuity, at 5150 km, is marked by a rapid increase in P - wave velocity and the occurrence of low velocity S - waves. The solid inner core has a density of ∼ 13 g/cm3. Density
and magnetic studies suggest that Earth ’ s
inner core also consists largely of iron, with nickel and less oxygen, sulfur and/or hydrogen than in the outer core. Seismic studies
have shown that the inner core is seismically anisotropic; that is, seismic velocity in the inner core is faster in one direction than in others.
Illustrate the cross-section of MOR-type Ophiolite, and explain how the layers are formed and arranged.
As the lithosphere is thinned, the asthenosphere rises toward the surface generating basaltic –
gabbroic melts. Melts that crystallize in magma bodies well below the surface form plutonic rocks such as gabbros that become layer 3 in oceanic crust. Melts intruded into near - vertical fractures above the chamber form the basaltic – gabbroic sheeted dikes that
become layer 2b. Lavas that flow onto the
ocean floor commonly form basaltic pillow
lavas that become layer 2a. The marine sediments of layer 1 are deposited atop the basalts. In this way layers 1, 2 and 3 of the oceanic
crust are formed. The underlying mantle consists of ultramafi c rocks (layer 4). Layered ultramafic rocks form by differentiation near the base of the basaltic – gabbroic magma bodies, whereas the remainder of layer 4 represents the unmelted, refractory residue that accumulates below the magma body.
Illustrate the different types of pull-apart basin and explain how they generally develop.
In places where such transform faults bend or where their tips overlap, deep pull - apart basins may develop in which thick accumulations of sedimentary rocks accumulate rapidly
Illustrate and explain how the Hawaiian Islands formed through hotspot, and explain the concept of its volcanism
Linear seamount chains, such as the Hawaiian Islands, are surface expressions of hotspots. At any one time, volcanism is restricted to that
portion of the plate that lies above the hotspot. As the plate continues to move, older volcanoes are carried away from the fixed hotspot and new volcanoes are formed above it. The
age of these seamount chains increases systematically away from the hotspot in the direction of plate motion.
Describe how the solar system formed through nebular theory.
The nebular theory states that the solar system was formed from the cloud of gas and dust called nebula. The formation started as these clouds start to contract and gravitational collapse. As materials are mostly concentrated at the center due to gravitational collapse, the protosun (early Sun) was formed. During the collapse, gravitational energy was converted into thermal energy leading to increased heating in the inner part of the nebula. The heat caused the dust to broke up into molecules and energetic atomic particles. However, at distances beyond the orbit of Mars, the temperature is relatively cool and the dust was covered with thin layers of ice of frozen water, methane, carbon dioxide, and ammonia. The formation of the Sun marked the end of contraction and gravitational heating. As the temperature starts to decline, the molecules where the inner planets reside were condensed into tiny particles and starts to coalesce (join together). Repetitive coalescence lead to the formation of asteroid-sized bodies called planetetisimals and ultimately the inner planets. Due to the inner planets’ low gravitational pull and high temperature, they cannot accumulate much of the lighter elements such as hydrogen and helium. Eventually, these light elements were swept by the solar winds away from the inner planets. By the time the inner planets are forming, the outer planets with their extensive satellite system began to develop. Due to their low temperature, these planets are mostly composed of ice, carbon dioxide, ammonia, and methane. Also, due to their high gravity, they can attract and hold large quantities of even lighest elements such as hydrogen and helium
Illustrate a flow diagram of the Life Cycle of a Star
Giant gas cloud and dust (nebula)
Protosun
T-Tauri Stage
Main Sequence
Red Giant (eventually leads to implosion)
Fusion of Heavier Elements
Supernovae
Create a table for the classification of Meteorites
- Stony Meteorites:
• Chondrites - Carbonaceous, Ordinary, Enstatite
• Achondrites - Primitive, Lunarian, Martian, Howardite-Eucrite-Diogenite (HED) - Stony-Iron Meteorites:
• Pallasites
• Mesosiderites - Iron Meteorites
Describe the parameters needed to consider a celestial body a planet, and a dwart planet. Give 3 examples of dwarf planets.
Planet
✓ is in orbit around the Sun
✓ has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape
✓ has cleared the neighborhood around its orbit.
Dwarf Planet
✓ is in orbit around the Sun
✓ has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape
✓ Has not cleared the neighborhood around its orbit.
✓ Not a satellite
Examples: Pluto, Eris, and Ceres
Illustrate the difference between Laminar and Turbulent flow.
Calculate the wetted perimeter and cross-sectional area of a stream channel with these following details: Width = 15m; Length = 3m.
Cross-sectional area = L × W 5m×2m = 10m²
Wetted perimeter = Width + 2Length = 5 + 2(2) = 9m
Explain how wetted perimeter affects the water flow velocity of a stream channel?
Wetted perimeter refers to the total length of the boundary that is in direct contact with water. The lesser the the wetted perimeter the lesser the frictional resistance/drag of a stream channel. Thus, the lesser the frictional resistance, the faster the water flow velocity.
Create a graph that shows how various properties of a stream
channel change from its headwaters to its mouth (Slope, Flow velocity, Size, Roughness, and Discharge).
Make an illustration that shows how streams transport their load of sediment in three
ways. Emphasize in the drawing the three types of movement of bed load.
Illustrate how oxbow lakes are formed.
What are the factors that affect alluvial channel’s pattern. What are the two common types of alluvial channel and differetiate them.
A channel’s pattern is influnced by the channel’s slope or gradient, average size of the particles being transported, and the discharge. Meandering channels develop where the load consists largely of fine-grained unconsolidated particles that are transported as suspended load in deep, relatively
smooth channels. By contrast, wide, shallow braided channels develop where coarse-grained alluvium is transported mainly as bed load.
Make a comparison table between Valley Widening and Valley Deeping
Valley Deeping: Energy is dominantly directed towards the bed of the channel; Abrasion by course-grained bedload; Rapids and waterfalls are common features; Dominant at bedrock channels or near/at headwaters; At zone of sediment production of a river system; Usually braided or straight; Steep valley walls (V-shaped).
Valley Widening: Energy is dominantly directed laterally or side to side of the bank; Abrasion by sand-sized suspended load; Cutbanks and floodplains are common features; Dominant at alluvial channel or near/at downstream; At zone of sediment transport/deposition of a river system. Usually meandering. Steep valley walls are far from the channel (\___/-shaped)
How incised meanders can be formed?
Incised meanders are channels that can found at narrow steep valleys. These meanders are formed due to uplift and dropped in base level. As the land gradually rises and the base level gradually drops, meandering channels begin to downcut its bed because of their steepining gradient.
