prelim Flashcards
How did the geosphere form
Formed through accretion, where dust and gas particles came together under gravity. Over time, these materials collided, forming Earth’s solid layers, including the crust, mantle, and core.
How did the atmosphere form
Through outgassing, gases like carbon dioxide, water vapor, and nitrogen were released from molten Earth during volcanic activity. Gravity retained these gases, forming the early atmosphere, while some dissolved in rain.
How did the hydrosphere form
from water vapor released during outgassing and water delivered by meteorites. As Earth cooled, water condensed to form oceans and other bodies of water. It’s a key part of Earth’s water cycle.
How do seismic waves help scientists understand Earth’s structure?
Seismic waves provide evidence for the Earth’s internal layers, revealing concentric shells: a thin outer crust, mantle, liquid outer core, and solid inner core.
What are the characteristics of L Waves (Rayleigh waves)?
Type: Surface waves.
Speed: Slowest, most destructive.
Medium: Travel only along the Earth’s surface.
How do meteorites provide evidence for Earth’s structure?
Meteorites contain early solar system particles, helping reveal the age, composition, and density of Earth from its accretion.
What do meteorites show about Earth’s composition?
What do meteorites show about Earth’s composition?
What do meteorites reveal about Earth’s density?
Meteorites help confirm that Earth’s core is denser than its mantle and crust, demonstrating layer differences.
Why are meteorites important to Earth’s formation?
They provide evidence of the accretion process and early material that formed Earth.
What is the composition and thickness of the crust?
Oceanic crust:
Composed of mafic rocks like basalt and gabbro; 6-7 km thick, denser than continental crust.
Continental crust:
Composed of felsic rocks like granite and andesite; 20-70 km thick, less dense.
What is the lithosphere and its characteristics?
Composed of minerals rich in iron, aluminum, silica, and magnesium. It’s solid and dense, ranging from 40-280 km thick.
What is the composition and thickness of the asthenosphere?
Made of peridotite (rich in olivine and pyroxene), it’s semi-molten due to high temperature and pressure. Thickness: 440 km.
at is the composition and thickness of the mantle?
Composed of silicates like olivine and pyroxene. It’s mostly solid but moves plastically over time. Thickness: 2900 km.
What are the characteristics of the core?
Outer core: Liquid, composed of iron and nickel, thickness: 2200 km.
Inner core: Solid, composed of iron and nickel, creates Earth’s magnetic field. Thickness: 1220 km.
What do zircon crystals reveal about Earth’s age?
Zircon crystals, composed of silicate are the oldest known minerals on Earth, with ages up to 4.40 billion years. This dating indicates that Earth must be at least this old.
How do radiometric techniques determine Earth’s age?
Uranium-lead dating measures the decay of uranium isotopes into lead isotopes, providing an age estimate for Earth of 4.45-4.55 billion years. This is based on the known half-life of uranium isotopes.
How did Aboriginal and Torres Strait Islander peoples classify rocks and minerals?
They classified rocks and minerals based on their use for tools, ceremonial purposes, and their role in defining a sense of place.
What are felsic minerals and their characteristics?
Composition: Rich in silicon and aluminium, may include potassium.
Color: Light-colored.
Density: Lower than mafic minerals.
Examples: Quartz, plagioclase, orthoclase, muscovite mica.
What are mafic minerals and their characteristics?
Composition: Rich in iron and magnesium.
Color: Dark-colored, ranging from green to black.
Density: Higher than felsic minerals.
Examples: Olivine, pyroxene, amphibole, biotite mica.
How is hardness used to classify minerals?
Hardness measures a mineral’s resistance to scratching, assessed using Mohs hardness scale, which ranks minerals from 1 (talc) to 10 (diamond).
What is the difference between cleavage and fracture in minerals?
Cleavage: Breaks along smooth, flat surfaces due to weak bonds in the crystal structure.
Fracture: Breaks along irregular, rough surfaces.
What does luster tell us about a mineral?
describes how light reflects off a mineral’s surface, categorized as vitreous, metallic, dull, or earthy.
How are color and streak used to identify minerals?
Color: General appearance; less reliable for identification.
Streak: The color of the powder left when a mineral is rubbed on a streak plate; more diagnostic.
How are igneous rocks formed?
From magma crystallizing. Intrusive (coarse-grained) cools slowly inside Earth; extrusive (fine-grained) cools quickly on the surface.
How do sedimentary rocks
From weathered materials like particles and clay. Clastic rocks come from rock fragments, while chemical rocks form from mineral precipitation.
How are metamorphic rocks formed?
From existing rocks subjected to high temperature and pressure. Foliated rocks show layers from pressure, while non-foliated rocks form with high temperature but low pressure.
What is soil and how is it formed?
Soil is weathered material at Earth’s surface, derived from parent rock. It forms through the interaction of atmospheric, geologic, hydrologic, and biotic processes.
What are the components of soil?
Mineral matter: From weathered parent rock.
Organic matter: Litter and decomposed materials.
Water: Fills pores between soil grains.
Air: Found in the soil’s pore spaces.
What are soil horizons and their characteristics?
O horizon: Surface layer of decomposed plant material.
A horizon: Topsoil, dark and loamy, with leaching.
B horizon: Subsoil, finer, denser, and more colorful.
C horizon: Weathered parent material.
D horizon: Below soil profile, differing from parent material.
What factors affect soil formation?
Climate
Topography
Organisms
Time
What is relative dating?
Order: Arranges geological events.
Method: Uses stratigraphy.
Result: Provides a relative age (older or younger).
What is absolute dating?
Exact Age: Calculates precise age.
Method: Measures physical properties.
Example: Radiocarbon dating using carbon isotopes and half-life.
What did Wegener contribute to the theory of plate tectonics?
Year of Work: Early 1900s
Answer: Proposed the idea of Pangea and continental drift. Provided evidence through the matching of fossils across continents and the jigsaw fit of coastlines. Initiated discussions about plate movement but lacked an explanation for how plates moved.
What was Holmes’ contribution to plate tectonics?
Year of Work: 1910-1965
Answer: Introduced the concept of convection currents in the mantle as the mechanism for plate movement. First used radiometric dating to measure rock ages, providing a mechanism that supported Wegener’s theory.
What did Hess propose regarding seafloor spreading?
Year of Work: 1962-1969
Answer: Developed the theory of seafloor spreading, which linked it to plate tectonics and unified geological understanding. His ideas were confirmed by later studies showing older rocks farther from mid-ocean ridges.
How did Vine and Matthews contribute to plate tectonics?
Year of Work: 1960s
Answer: Mapped seafloor magnetic anomalies and demonstrated symmetrical magnetic reversals on either side of mid-ocean ridges, confirming seafloor spreading and providing evidence for plate movement.
What was the role of the Glomar Challenger in plate tectonics research?
Year of Work: 1968-1983
Answer: Conducted deep-sea drilling that provided evidence for the age of oceanic crust, confirming the theory of seafloor spreading by showing that the ocean floor’s age increases with distance from mid-ocean ridges.
What occurs at divergent boundaries with oceanic plates?
: Oceanic-Oceanic
Answer: Two oceanic plates move apart, allowing magma to rise and form new oceanic crust. This leads to the creation of mid-ocean ridges, with high volcanic activity and shallow-focus earthquakes.
