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Which branch of geology focuses on the work of natural processes that change the Earth's surface?
The oldest era in the geologic time scale is known as the Cenozoic era.
False
What is the largest division in the geological time scale?
Eon
The __________ is the lowest layer of the atmosphere.
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Match the following geologic time divisions with their correct order:
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Which type of volcanic eruption is characterized by moderate bursts of expanding gases that eject clots of incandescent lava?
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Pyroclastic flows are associated with explosive volcanic eruptions.
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Name one type of volcanic hazard that can result from a volcanic eruption.
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The process of turning sediments into sedimentary rocks through compaction and ______ is known as lithification.
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Match the type of volcanic eruption with its characteristic:
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Which of the following is NOT a key factor in the identification of depositional environments?
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The soil profile consists of layers that provide insight into soil formation processes.
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List the five factors affecting soil formation according to the CLORPT model.
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The combination of mineral content and sedimentary texture of the rock is known as __________.
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Match the types of depositional environments with their categories:
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Which type of sedimentary rock is formed from pieces of rock that have been mechanically weathered?
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Chemical weathering involves the physical breakdown of rocks.
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What is the primary cause of mass wasting?
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The process of forming sedimentary rock by the accumulation of organic debris is called __________ sedimentary rocks.
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Match the following types of weathering with their descriptions:
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Which factor does NOT influence the rate of weathering?
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Depositional environments refer to the places where sediments are eroded.
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Name two types of erosion.
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What process explains the movement of continents on Earth's surface?
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The oceanic crust is less dense than the continental crust.
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What separates the upper and lower crust of the Earth?
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The layer of water surrounding the lithosphere is known as the __________.
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Match the following Earth layers with their characteristics:
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Which of the following best describes sea floor spreading?
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The Mid-Atlantic Ridge separates the North American plate from the Eurasian plate.
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Who proposed the idea of Catastrophism?
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The __________ Discontinuity marks the transition between the crust and the mantle.
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Which type of crust primarily forms the continents?
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Study Notes
Geology as a Discipline
- Geology is an interdisciplinary field that studies the Earth's physical structure.
- Two main branches of geology: Physical Geology and Historical Geology.
- Physical Geology focuses on natural processes that change the Earth's surface.
- Historical Geology studies the Earth's geologic past.
Importance of Geology to Civil Engineering
- Geology is crucial for civil engineering projects to understand ground conditions, identify potential hazards, and design safe and sustainable structures.
- Civil engineers rely on geological data to assess: soil stability, rock types, groundwater levels, earthquake risks, and other geological factors.
- Understanding geologic processes helps civil engineers mitigate risks such as landslides, subsidence, flooding, and erosion.
- Applying geology principles ensures structures are built safely and efficiently.
Earth's Systems
- Earth's history is divided into four major divisions in abstract time: Eons, Eras, Periods, and Epochs.
- The largest division is the Eon.
- The four Eras, from oldest to youngest, are the Precambrian, Paleozoic, Mesozoic, and Cenozoic.
- Each Era is further subdivided into Periods, and Periods into Epochs.
The Geologic Time Scale
- The Geologic Time Scale is a standardized timeline that portrays the history of the Earth.
External Structure of the Earth
- Earth consists of several spheres:
- Atmosphere: The layer above the lithosphere and hydrosphere.
- Biosphere: The "zone of life" encompassing all living organisms.
- Cryosphere: Contains large ice masses at the poles and elsewhere.
- Geosphere/Lithosphere: Also known as "land."
- Hydrosphere: The layer of water surrounding the lithosphere.
Internal Structure of the Earth
- The Earth has three main layers:
- Crust: The outermost solid layer.
- Mantle: A thick layer of mostly solid rock below the crust.
- Core: The Earth's center, consisting of a solid inner core and a liquid outer core.
Discontinuities in the Earth's Layers
- Discontinuities mark boundaries between Earth's layers:
- Conrad Discontinuity: Separates the upper and lower crust.
- Mohorovicic Discontinuity: Transition zone between the crust and the mantle.
- Repetti Discontinuity: Separates the upper mantle from the lower mantle.
Theories: Uniformitarianism vs. Catastrophism
- Uniformitarianism (James Hutton): "The Present is the Key to the Past."
- Uniformitarianism assumes that natural laws haven't changed throughout Earth's history.
- Catastrophism (Baron Georges Cuvier): Emphasized sudden, catastrophic events as the primary drivers of geologic change.
Plate Tectonics
- Continental Drift Theory: Proposed by Alfred Wegener in 1912, suggesting continents shift positions on Earth's surface.
- Seafloor Spreading: The process where new lithosphere is created at divergent plate boundaries, forming new crust.
- Mid-Ocean Ridge: Large mountain ranges on the ocean floor where seafloor spreading occurs.
Crusts
- Continental Crust: Forms continents and continental shelves.
- Composed mostly of granite.
- Lighter than oceanic crust.
- Oceanic Crust: The uppermost layer of the oceanic portion of tectonic plates.
- Composed mostly of basalt.
- Denser than continental crust.
Volcanic Eruptions
- Different types of volcanic eruptions:
- Icelandic: Form lava plateaus.
- Hawaiian: Form shield volcanoes with gentle slopes.
- Strombolian: Moderate bursts of gas ejecting lava clots.
- Vulcanian: Dark, turbulent eruptions with expanding gas clouds.
- Pelean: Explosive outbursts generating pyroclastic flows.
- Plinian: Intensely violent eruptions.
Volcanic Hazards
- Potential hazards from volcanic activity:
- Tephra/Ash: Volcanic debris that can fall as a hazard.
- Lava Flows: Molten rock that can flow and damage areas.
- Pyroclastic Density Currents: Hot, high-speed flows of volcanic material.
- Pyroclastic Falls: Deposition of volcanic material from the air.
- Lahars: Mudflows made up of volcanic debris.
- Volcanic Gases: Can be toxic and lethal.
- Volcanic Landslides: Large-scale collapses of volcanic slopes.
- Climate Change: Volcanic eruptions can influence global climate.
Mitigating Volcanic Hazards
- Essential steps to mitigate volcanic risks:
- Understanding volcano behavior.
- Knowing how volcanic hazards behave.
- Implementing strategies to avoid or minimize hazards.
Sedimentary Rocks
- Sedimentary rocks form from the accumulation and lithification of sediments.
- Processes involved in their formation: weathering, transport deposition, compaction, and cementation.
- Sedimentary rocks are the only type of rock that typically contain fossils.
Types of Sedimentary Rocks
- Classification based on origin:
- Clastic/Detrital: Formed from fragments of other rocks (clasts).
- Chemical: Precipitation of minerals from a fluid.
- Organic: Formed from accumulated organic debris.
Soil Formation; Weathering Products
- Weathering: The breakdown of rocks at or near the Earth's surface.
- Types of weathering: Mechanical/Physical, Chemical, and Biological.
Factors Influencing Weathering Rates
- Key factors that affect weathering rates:
- Temperature.
- Rock type.
- Moisture availability.
Erosion
- Erosion is the removal and transport of weathered material by agents like water, wind, ice, or gravity.
- Mass wasting: Movement of rock or soil downslope primarily due to gravity.
Types of Erosion
- Fluvial Erosion: Erosion by water.
- Aeolian Erosion: Erosion by wind.
- Glacial and Periglacial Erosion: Erosion by ice.
- Gravitational Erosion (Mass Wasting):
- Rock falls.
- Landslides.
- Debris/Mud flows.
- Slumps.
- Creep.
Deposition
- Deposition is the process by which weathered and eroded materials are settled in a new location.
Depositional Environments
- Depositional environments are locations where sediments are deposited.
- Influence characteristics of sedimentary rocks, such as lithology, minerals, texture, structures, and fossils.
Keys to Identifying Depositional Environments
- Identifying features that help determine depositional environments:
- Lithology: The mineral composition and texture of the rock.
- Sedimentary Structures: Patterns within sedimentary rocks that provide information about depositional processes.
- Fossils: Remains or traces of organisms preserved in rocks.
Types of Depositional Environments
- Classification of depositional environments:
- Continental/Terrestrial.
- Marginal Marine/Transitional.
- Marine.
Factors Affecting Soil Formation
- Soil formation is influenced by:
- CLORPT:
- Climate: Temperature and precipitation.
- Organic Matter: Decomposed plant and animal material.
- Relief/Topography: The slope and shape of the land.
- Parent Materials: The underlying rock or sediment.
- Time: The length of time soil has been developing.
- CLORPT:
Soil Properties
- Characteristics used to describe soil:
- Color: Reflects composition and mineral content.
- Structure: The arrangement of soil particles.
- Texture: The relative proportions of sand, silt, and clay.
Soil Profile
- A soil profile is a vertical section of soil, revealing different horizons with distinct characteristics.
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Description
This quiz covers the interdisciplinary field of geology, its main branches, and its critical importance to civil engineering. Discover how geological understanding influences engineering projects, ensuring safety and sustainability. Explore Earth's systems and geological time divisions as foundational knowledge for civil engineers.
