Geological Time Scale, Dating Methods, and Earth History
Geological Time Periods and Key Events
Paleozoic Era
- Cambrian: Marine invertebrates with external skeletons.
- Ordovician: First vertebrates appear.
- Silurian: First jawed fish; first land plants.
- Devonian: First amphibians.
- Carboniferous: Forests of giant ferns; first reptiles.
- Permian: Pangaea forms. The climate became very dry toward the end, leading to the greatest mass extinction event.
Mesozoic Era
- Triassic: First dinosaurs; first mammals.
- Jurassic: Gymnosperm plants dominate; first birds appear.
- Cretaceous:
Mineral Properties and the Complete Rock Cycle Explained
Mineral Properties and Formation
Origin of Minerals
The origin of minerals can be:
- Within a mass of molten rock (magma), such as feldspar or olivine.
- Within solid rocks under high pressures and temperatures, such as calcite.
Properties of Minerals
- Color
- The type of light a mineral reflects when illuminated.
- Luster (Brightness)
- The way a mineral reflects light (e.g., metallic, glassy, dull).
- Hardness
- The resistance of a mineral to being scratched.
- Streak (Color of the Line)
- The color of the dust that occurs when
Environmental Science Concepts: Resources, Pollution, and Ecosystem Dynamics
1. Resource Definitions and Pollution Classification
1.1 Resource Definitions
Define:
- (a) Renewable resources: Resources that are naturally replenished.
- (b) Non-renewable resources: Resources that exist in fixed amounts and are not naturally replenished on a human timescale.
1.2 Classification of Pollutants
(A) Depending upon their nature of existence:
- Quantitative: Normally occurring in nature.
- Qualitative: Do not normally occur.
(B) Depending upon the form in which they persist after being released in
Read MoreEarth History: Ecological Succession and Plate Tectonics
Ecological Succession and Climax Communities
Ecological succession is the process by which certain populations are replaced by new ones to eventually form a climax community. A climax community occurs when a population reaches a stable composition and no longer undergoes significant changes.
Types of Succession
- Primary Succession: Occurs on virgin terrain where no previous community existed.
- Secondary Succession: Established on an existing biological community that has been eliminated by events such
Understanding Environmental Problems and Their Impact
Environmental Problems
Environment: is everything that affects living organisms.
Ecology: is the biological science that studies the relationship between living organisms.
Environmental problems include:
Ozone depletion, acid rains, and smogs.
Ozone (O3):
– Highly reactive gas – harmful to breathe – 3 atoms of oxygen.
1- 90% of the O3 is in the stratosphere, and it is called the ozone layer.
2- O3 absorbs a band of ultraviolet (UV) radiation called UVB.
Ozone Layer (O3):
– A region of Earth’s stratosphere
Earth’s Atmosphere: Protective Functions, Circulation, and Pollutants
Functions of the Atmosphere
- Protective Shield: The ozone layer in the stratosphere prevents most harmful ultraviolet (UV) radiation from reaching Earth’s surface. The atmosphere also protects against the impact of meteorites and other celestial bodies, which disintegrate upon entering its layers.
- Involvement in the Water Cycle: The atmosphere plays a crucial role in the water cycle. Water vapor condenses to form clouds, which then precipitate as rain or snow.
- Source of Life-Sustaining Gases: It contains