Year 11 ATAR Earth & Environmental Science Study Notes

Identification and Facts

Approximate Age of the Earth
- Estimated to be approximately 4.6 billion years.
Major Layers of Earth
- Continental Crust
- Oceanic Crust
- Moho Discontinuity (Boundary between crust and mantle)
- Upper Mantle
- Lower Mantle
- Gutenberg Discontinuity (Boundary between mantle and outer core)
- Outer Core
- Lehmann Discontinuity (Boundary between outer core and inner core)
- Inner Core
State of Each Internal Layer
- Continental Crust: Solid
- Oceanic Crust: Solid
- Upper Mantle: Solid (but can flow slowly)
- Lower Mantle: Solid
- Outer Core: Liquid
- Inner Core: Solid
General Composition of Layers
- Core: Composed of metallic elements (primarily iron and nickel)
- Mantle and Crust: Comprised of silicates
P-waves and S-waves
- P-waves (Primary waves):
- Type: Longitudinal
- Characteristics: Can travel through solids and liquids
- S-waves (Secondary waves):
- Type: Transverse
- Characteristics: Can only travel through solids
- Diagrams to support characteristics should be included.
Types of Evidence for Earth’s Internal Structure
- Seismic Evidence: Analysis of how seismic waves travel reveals information about layer states and properties.
- Meteorites: Composition of meteorites provides parallels to Earth's core material.
- Direct Observation: Limited direct observation of Earth's interior through geological studies.
Main Gases in Earth’s Original Atmosphere
- Dominated by gases such as water vapor, carbon dioxide, nitrogen, and methane.
Major Gases in the Modern Atmosphere
- Approximate Percentages:
- Nitrogen (N₂): ~78%
- Oxygen (O₂): ~21%
- Argon (Ar): ~0.93%
- Other gases (including CO₂ and trace gases): <1%
Atmospheric Layers
- Troposphere: Lowest layer, weather phenomena occur here.
- Stratosphere: Contains the ozone layer, prevents UV radiation from reaching Earth's surface.
- Mesosphere: Above the stratosphere, where meteors burn upon entering atmosphere.
- Thermosphere: Uppermost layer, temperature increases significantly with altitude.

Descriptions and Processes

Formation of the Solar System and Earth
- Formed from a solar nebula consisting of gas and dust, which collapsed under its own gravity, leading to the formation of the Sun and surrounding planets.
Planetary Differentiation
- Process by which denser materials sunk to the center of Earth, resulting in a layered structure based on density and composition.
Seismic Wave Behavior
- The behavior of seismic waves indicates the presence of a solid inner core and a liquid outer core, based on their speed and type of wave transmission.
Meteorite Composition
- Meteorites suggest Earth has a similar composition to certain meteorites, supporting the understanding of Earth's internal structure.
Formation of Earth’s Early Atmosphere
- Volcanic Outgassing: Released gases such as water vapor, carbon dioxide, sulfur dioxide, and nitrogen, contributing to the early atmosphere.
Contribution of Volcanoes to Water Formation
- Early volcanic activity released significant amounts of water vapor that eventually condensed to form oceans.
Changes in Atmospheric Composition Over Time
- Changes due to geological and biological activity (notably photosynthesis), reducing CO₂ levels and increasing O₂ levels over billions of years.
Oxygenation of the Atmosphere
- Photosynthetic organisms such as cyanobacteria produced oxygen, leading to an increase in atmospheric oxygen levels, known as the Great Oxidation Event.
Formation of Banded Iron Formations (BIFs)
- Formed in ancient oceans as iron dissolved in seawater reacted with oxygen produced by photosynthesis, resulting in sedimentary deposits of iron oxide.
Temperature Changes with Altitude in Atmospheric Layers
- Temperature varies inversely in the troposphere (decreases with altitude) and increases in the stratosphere due to the ozone layer, while values in the thermosphere are significantly higher due to solar radiation absorption.