Earth’s Past: A Geological Journey Through Time
ITEM 13: Getting the Earth and its Past
Readers Rock
In the development of geology as a science, three key ideas have been central:
- The Earth is immensely old. The Earth originated about 4,560 Ma; however, for many centuries, it was thought to be scarcely 6,000 years old.
- The Earth is constantly changing. The Earth’s surface changes permanently due to slow, gradual processes such as mountain erosion or continental movement, but also thanks to sporadic and intense processes, such as volcanic eruptions,
Geologic Time Scale: A Comprehensive Guide to Earth’s History
1. Principle of Superposition: When any given stratum was being formed, all the matter resting on it was fluid. Therefore, when the lowest stratum was formed, none of the upper strata existed.
2. Principle of Original Horizontality: Strata which are either perpendicular to the horizon or inclined to it were at one time parallel to the horizon.
3. Principle of Lateral Continuity: When any given stratum was being formed, it was either encompassed at its edges by another solid substance or it covered
Earth’s Interior: Composition, Seismic Waves, and Plate Tectonics
Earth’s Interior
Composition of Earth’s Interior
Direct Methods: Surveys (max. 13km), analysis of meteorites, analysis of lava from volcanoes (crust and mantle materials).
Indirect Methods: Studying Earth’s density (compared to the theoretical density of crustal material), studying seismic waves (behavior of primary and secondary waves).
Why is the outer core liquid and the inner core solid?
Iron Core = 90% + 10% nickel. Core temperature is 5000°C. At these temperatures, these materials are molten;
Read MoreEarth’s Hydrosphere: Composition, Processes, and Contamination
Life on Earth directly depends on water. Civilizations have disappeared, and many ecosystems have been affected by changes in water quantity and quality.
The ocean represents 97.2% of the hydrosphere, while ice in the polar caps accounts for 2.1%. Groundwater and water in lakes and rivers account for 0.6%. The remaining 0.1% is saline (potable) water found in lakes or groundwater.
The Hydrosphere
The hydrosphere is in close contact with the Earth’s lithosphere; therefore, their properties are related.
Read MoreLandform Classification: A Comprehensive Guide to Terrain
1. Landscape and Relief
The appearance of the Earth’s surface, excluding biotic elements, is represented in topographic maps.
1.1. Descriptive Landform Classification
Landforms are classified based on their appearance:
- Mountain: An isolated relief with a significant gap between its base and peak.
- Hill: An isolated relief with slight unevenness.
- Gorge/Throat: A narrow valley with steep walls.
- Plateau: An isolated, flat-topped topography.
- Terrace: A step-like relief.
1.2. Landform Classification by Formation
Read MoreAir Pollution: Dynamics, Effects, and Mitigation
Factors Influencing Pollutant Dispersion
Pollutant dispersion and concentration are influenced by emission characteristics, weather conditions, and geographical/topographical features. The pollutant’s nature, concentration, temperature, and physicochemical properties play a crucial role. When gas emissions exceed the average, weather conditions facilitate dispersion.
Atmospheric Conditions
The atmosphere’s state determines air mass movement and stability, influencing pollution spread. Key factors
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