Podcast
Questions and Answers
Which type of seismic wave is also known as a compressional wave?
Which type of seismic wave is also known as a compressional wave?
During which geologic era do we currently live?
During which geologic era do we currently live?
Which feature represents the edge of the continental crust?
Which feature represents the edge of the continental crust?
What is the primary cause of earthquakes?
What is the primary cause of earthquakes?
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What do we call the point on the Earth's surface that is directly above the focus of an earthquake?
What do we call the point on the Earth's surface that is directly above the focus of an earthquake?
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What percentage of the Earth's surface is occupied by oceans?
What percentage of the Earth's surface is occupied by oceans?
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What are mountain roots?
What are mountain roots?
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What is the primary concept explained by the elastic rebound theory?
What is the primary concept explained by the elastic rebound theory?
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What is formed when divergent boundaries occur?
What is formed when divergent boundaries occur?
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Which process transforms existing rocks into metamorphic rocks?
Which process transforms existing rocks into metamorphic rocks?
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What type of rock is characterized by high silica content?
What type of rock is characterized by high silica content?
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What occurs at convergent boundaries?
What occurs at convergent boundaries?
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Which is NOT a feature associated with convergent boundaries?
Which is NOT a feature associated with convergent boundaries?
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How many major lithospheric plates does the Earth's lithosphere have?
How many major lithospheric plates does the Earth's lithosphere have?
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What is the main component of rocks?
What is the main component of rocks?
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Who proposed the theory of continental drift?
Who proposed the theory of continental drift?
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Which feature differentiates oceanic crust from continental crust?
Which feature differentiates oceanic crust from continental crust?
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What type of rock is formed from the solidification of molten magma or lava?
What type of rock is formed from the solidification of molten magma or lava?
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What is the primary composition of the outer core of the Earth?
What is the primary composition of the outer core of the Earth?
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How does the lithosphere move in relation to the asthenosphere?
How does the lithosphere move in relation to the asthenosphere?
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What characteristic allows the asthenosphere to facilitate tectonic plate movement?
What characteristic allows the asthenosphere to facilitate tectonic plate movement?
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What occurs at the boundaries of tectonic plates?
What occurs at the boundaries of tectonic plates?
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Which type of igneous rock forms from magma that crystallizes slowly beneath the Earth's surface?
Which type of igneous rock forms from magma that crystallizes slowly beneath the Earth's surface?
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What is the role of the inner core in relation to the Earth's structure?
What is the role of the inner core in relation to the Earth's structure?
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Study Notes
Earth’s Surface Composition
- 29% of Earth’s surface is land and 71% is ocean.
- Continental shelf area increases the land area to 35% and decreases the ocean basin area to 65%.
Oceanic Relief Features
- Mid-oceanic ridge with a central rift where crust is pulled apart.
- Continental shelves accumulate thick deposits of continental sediments.
- Continental slopes are the edge of the continental crust.
- Oceanic trenches are where oceanic crust slides beneath continental crust.
Continents
- Divided into active mountain-making belts and inactive regions of old, stable rock.
- Continental shields and mountain roots are two types of stable structures.
- Mountain Roots are the deep, stable portions of the Earth's crust that support mountain ranges.
Time Scale
- Time older than 570 million years (MY) is Precambrian time.
- Three eras of time follow: Paleozoic, Mesozoic, and Cenozoic.
- Geologic eras are subdivided into periods.
- We live in the Holocene period (the last 12,000 years).
Earthquakes
- Shaking and trembling caused by rock movement beneath Earth's surface.
- Most severe earthquakes occur near plate collision boundaries.
- Earthquakes are the sudden release of stored energy.
- Result of fast movement between two blocks of rock.
- Released energy radiates away from the earthquake.
- Main cause of earthquakes is faults on the Earth's crust.
- A fault is a break between two blocks of rocks.
Earthquake Terminology
- The origin of the earthquake (where the fault begins) is the focus or hypocenter.
- The point on the Earth's surface directly above the focus is the epicenter.
Elastic Rebound Theory
- Explains how energy is stored in deformed rocks along fault lines and released during an earthquake.
- Seismic waves are vibrations that travel through Earth carrying energy released during an earthquake.
Seismic Waves
- Two types of waves produced during an earthquake.
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Body waves: travel through Earth’s interior.
- P wave (primary): compressional wave that causes alternate compression and expansion of the rock.
- Surface waves: travel along the Earth’s surface.
Metamorphic Rocks
- Created when existing rocks are transformed by heat, pressure, or chemically active fluids.
- This process, known as metamorphism, changes the mineral composition and structure.
Earth's Composition
- 91 elements occur naturally in the Earth’s crust.
- Eight elements make up more than 98 percent of the earth’s crust.
- A mineral is a naturally occurring, inorganic solid with a characteristic chemical composition and a crystalline structure.
- Felsic rocks (comprising the crust) are high in silica content.
- **Ultramafic rocks **(comprising the mantle) are high in magnesium and iron content.
Plate Tectonics
- The theory proposed by Alfred Wegner in 1912 suggests that the crustal plates are moving over the mantle.
- Wegner proposed that today’s continents once formed a single landmass, called Pangaea.
- The uppermost mantle and the overlying crust behave as a strong, rigid layer, known as the lithosphere, which is broken into segments called plates.
Lithospheric Plates
- The Earth’s lithospheric shell is divided into six great lithospheric plates and at least nine lesser plates.
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Divergent boundaries (Constructive): two plates slide apart from each other. They are characterized by:
- Rift valleys
- Tilted block mountains
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Convergent boundaries (Destructive): two plates slide towards each other, forming either a subduction zone or a continental collision. They are characterized by:
- Trenches
- Mountain ranges
- Island arcs
- Volcanic arcs
- Transform boundaries (Conservative): plates slide past each other along transform faults.
Earth Structure and Composition
- The layers of the Earth’s interior include the crust, mantle, liquid outer core, and solid inner core.
- Crust: outermost layer, thinnest and solid, composed of continental and oceanic crust.
- Mantle: thick layer beneath the crust, semi-solid rock that flows slowly.
- Outer Core: Liquid layer beneath the mantle, composed mainly of iron and nickel.
- Inner Core: innermost layer, solid sphere due to high pressure, primarily iron and nickel.
Lithosphere and Asthenosphere
- Lithosphere: rigid outer layer of Earth (crust + upper mantle).
- Asthenosphere: semi-fluid layer of the upper mantle beneath the lithosphere.
Rocks
- Rocks are aggregates of mineral particles.
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Igneous Rocks: formed from the solidification of molten magma or lava.
- Intrusive (Plutonic): crystallize slowly beneath the Earth's surface.
- Extrusive (Volcanic): erupt and cool quickly on the surface.
- Sedimentary Rocks: formed from the accumulation and compaction of sediments.
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Description
Explore the composition of Earth's surface and the various geological features found within our oceans and continents. This quiz covers land-to-ocean ratios, oceanic relief features, and the geological timescale, including major eras and periods. Test your knowledge about the Earth's structure and its history!