Questions and Answers
Which layer of the Earth is composed primarily of an iron-nickel alloy?
What characterizes the Oceanic Crust compared to the Continental Crust?
Which layer of the Earth is defined as soft and weak, allowing for deformation?
What is the estimated thickness of the Lithosphere?
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At what depth does the Mantle extend to below the Earth's Crust?
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What primarily separates the Earth's crust from the underlying mantle?
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Which materials are primarily thought to compose Earth's core?
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What is the main driving force for plate movement according to scientists?
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Which of the following mechanisms involves the sinking of cold ocean lithosphere?
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What describes the behavior of the hot, solid rock in the mantle?
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Study Notes
Earth's Internal Structure
- Earth is divided into three main layers: the Crust, Mantle, and Core, based on chemical composition.
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Crust: Thin outer layer, ranges from 7 km (oceanic) to 70 km (continental) in thickness.
- Oceanic Crust: Basaltic composition, density ~3.0 g/cm³, younger (up to 180 million years).
- Continental Crust: Composed mainly of granitic rocks, density ~2.7 g/cm³, can be as old as 4 billion years.
- Mantle: Extends to about 2900 km depth; upper mantle composed mainly of peridotite.
- Core: Dense center of Earth, radius ~3486 km, primarily an iron-nickel alloy, density nearly 11 g/cm³.
Physical Properties of Earth's Layers
- Lithosphere: Rigid outer shell (crust and uppermost mantle), approximately 100 km thick.
- Asthenosphere: Soft, malleable layer beneath lithosphere, extending to about 660 km depth.
- Lower Mantle: Rigid layer from 660 to 2900 km, rocks are hot and can flow gradually.
- Outer Core: Liquid layer contributing to Earth's magnetic field, up to 2270 km thick.
- Inner Core: Solid inner sphere with a radius of 1216 km.
Discovery of Earth's Layers
- Mohorovičić Discontinuity (Moho): Boundary separating crust from mantle; seismic waves increase velocity below 50 km depth.
- Composition of the mantle is based on indirect evidence, with lava eruptions providing insights into asthenosphere composition.
- Earth's core is inferred to be composed mainly of dense iron and nickel.
Mechanisms of Plate Motion
- Plate movement is primarily driven by mantle convection, involving convection currents due to density differences.
- Convection Current: Continuous fluid flow caused by temperature and density variations.
- Whole mantle convection describes the upward movement of rock from lower to upper mantle, taking millions of years.
Factors Driving Plate Motion
- Slab-Pull: Mechanism where cooler, denser oceanic crust sinks into the mantle, pulling the trailing lithosphere.
- Ridge-Push: Oceanic lithosphere slides down the sides of mid-ocean ridges due to gravity.
- Mantle Plumes: Heat anomalies that rise towards the surface, potentially causing volcanic activity.
Learning Tasks Overview
- Identify layers within Earth’s structure.
- Sequence the arrangement of Earth's internal layers based on their depth.
Key Concepts
- Convection: Flow in heated fluids due to temperature and density differences.
- Slab-Pull and Ridge-Push: Key drivers of tectonic movements; linked to gravitational effects on oceanic lithosphere.
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Description
Engage in this self-directed learning activity focused on Earth's internal heat and structure. This module will help you describe the origins of Earth's internal heat and understand the layers of the Earth. Perfect for Grade 11 and 12 students studying Earth and Life Science.
