F4.1 Earth Structure
Introduction
Recap of the internal structure of the Earth.
Understand how geologists gather evidence about Earth's interior.
Page 1: Understanding the Internal Structure of Earth
Objective to deepen understanding of Earth's internal structure.
Overview of geologists' methods to investigate the Earth's interior.
Page 2: The Hypsographic Curve
Mountain heights: Mt. Everest = 8850 meters.
Land comprises 29.2% of Earth's surface; oceans cover 70.8%.
Average elevation of land is approximately 840 meters.
Average depth of oceans is about 3729 meters.
Deep ocean regions and trenches, like the Mariana Trench (11,022 meters), are highlighted.
Page 3: Distribution of Elevations
Hypsographic curve visualizes cumulative elevations of Earth's surface.
Key elevation groupings:
Continents: typically hundreds of meters above sea level.
Oceanic abyssal plains: approximately 4300 meters below sea level.
Differences in oceanic and continental crust structure confirmed by research.
Dynamic Earth processes prevent erosion and sediment accumulation over long periods.
Page 4: Interest in Other Planets
Exploration of surfaces of Venus, Mars, and the Moon compared to Earth.
Characterization of planetary elevations through Gaussian distribution.
Page 5: Major Features of Earth's Surface
Major geological features discussed:
Oceanic Crust (20-65 Ma, 65 Ma).
Geological provinces such as shields, platforms, orogens, basins, and large igneous provinces.
Page 7: Structure of Earth
Illustrates Earth’s structure:
Crust: outer layer, contains continents, mountains, and oceans.
Mantle: extends beneath the crust.
Core: innermost part consisting of inner and outer cores.
Page 9: Tectonic Plate Interaction
Description of crust and mantle interactions due to tectonic activity.
Explains magma movement and tectonic currents.
Page 10: Earth's Structure
Overview of Earth's layers:
Crust (oceanic and continental): granitic and basaltic rocks.
Lithosphere: rigid outer shell.
Asthenosphere: softer layer beneath the lithosphere.
Mesosphere: lower mantle features.
Outer core: liquid; inner core: solid.
Page 11: Oceanic Crust Details
Oceanic crust characteristics:
Solid rock: up to 35km thick.
Composed mainly of basalt.
Higher density (3 g/cm³), therefore young in geological terms (rarely older than 200 million years).
Page 13: Continental Crust Overview
Continental crust properties:
Thicker than oceanic crust (average 40km).
Composed of various rocks, primarily granitic (felsic materials).
Lower density (2.7 g/cm³); older history (up to 3.7 billion years).
Page 15: Discontinuities in Earth's Layers
Explanation of discontinuities, signifying changes in physical or chemical properties of rocks:
Conrad Discontinuity, Moho Discontinuity, Repetti Discontinuity, Gutenberg Discontinuity, and Lehmann Discontinuity.
Page 18: Asthenosphere Characteristics
Lithosphere and asthenosphere:
Lithosphere: rigid layer of the crust and upper mantle.
Asthenosphere: semi-fluid layer allowing for tectonic movement.
Low-velocity zone signifies mantle properties where rocks begin to partially melt.
Page 21: Upper Mantle Composition
Upper mantle:
Consists of solid silicates, primarily peridotite.
Radioactive decay contributes to Earth's heat source.
Page 22: Lower Mantle Properties
Lower mantle:
Remains solid due to intense pressure.
Contains heavier silicates, resembling stony meteorites.
Page 24: Understanding the Outer Core
Characteristics of the outer core:
Composed mainly of liquid iron and nickel, creating reduced rigidity.
Temperature and pressure conditions result in its liquid state.
Page 26: Inner Core Description
Inner core:
Solid state, composed primarily of iron (with some nickel).
Experiences extreme pressure (3.6 million times Earth’s surface pressure).
Density approximately 12 g/cm³.
Conclusion
Understanding the internal structure is key to grasping Earth's geological activity.
Discontinuities and the differences between crust types provide insights into tectonic processes.