A Comprehensive Guide to Earth Sciences: From Rocks to Volcanoes
Discharge and Erosion
Discharge (m3/s) = width (m) x depth (m) x velocity (m/s)
Erosion produces stream load, the combination of:
- Bed load (gravel, sand – roll, bounce, slide)
- Suspended load (silt, clay – float)
- Dissolved load (dissolved minerals)
Flood Management
Flood Prevention: Try to control the flow and stage of water.
Flood Adjustment: Policy and lifestyle shift to account for local flooding.
Groundwater and Aquifers
Porosity: Proportion of earth material made up of spaces (that can fill with water)
Permeability: Capacity of water to flow through earth materials
Groundwater is stored in bodies of rock and/or sediment termed aquifers.
Aquifers have good porosity and permeability:
- Good aquifer materials = sand, gravel, sandstone, and fractured rocks
Aquitard = opposite of aquifer (materials with poor porosity, permeability – clay, shale)
Minerals and Silica Content
Minerals with low silica content share no or few oxygens and have simple structures (independent, chains) − Olivine, amphibole
Minerals with high silica content share more oxygen atoms and have more complex structures (sheets, framework) − Quartz, feldspar
Felsic Minerals and Magma
Silica-rich (FELSIC) minerals: quartz, feldspar (light-colored); Framework silicates (complex structures)
Felsic magma produces Rhyolite/Granite
Mafic Minerals and Magma
Silica-poor (MAFIC) minerals: olivine, pyroxene, biotite (dark-colored); Isolated, single-chain silicates (simple structures)
Mafic magma produces Basalt/Gabbro
Types of Sedimentary Rocks
Three types of sedimentary rocks:
- Clastic (e.g., sandstone, shale) – the result of weathering processes
- Chemical (e.g., rock salt, gypsum) – environmental chemistry
- Biochemical (e.g., limestone, coal, chalk) – formed from shells and bodies of underwater organisms
Faults and Stress
- If the hanging wall is lower than the footwall = normal fault (stress: pull apart)
- If the hanging wall is higher than the footwall = reverse fault (stress: push together)
Earthquake Magnitude and Intensity
Magnitude: a standard measure of the shaking and/or energy released from an earthquake calculated by using seismic waves on a seismogram
Intensity: a measure of the effects of an earthquake on people and buildings (damage)
Seismic Waves
Body waves: travel through Earth’s interior
Surface waves: travel at Earth’s surface (do the most damage)
Types of Volcanoes
- Composite or Stratovolcano (convergent) → More viscous lavas, much explosive (pyroclastic) debris; large, emitted from a central vent
- Volcanic Dome → Very viscous lava; relatively small; commonly occurs adjacent to craters of composite volcanoes
- Shield Volcano→ Low viscosity liquid lava emitted from a central vent; mostly produces lava; large
- Scoria or Cinder cone → Explosive liquid lava; small; potentially high gas content
Oil and Natural Gas Formation
Oil and natural gas form from dead algae.
Types of Unconformities
Angular Unconformity: Older tilted rocks are covered by younger horizontal ones, showing erosion and a time gap.
Nonconformity: Sedimentary rocks on top of older igneous or metamorphic rocks, indicating erosion and a change in environment.
Disconformity: Break between parallel sedimentary layers, indicating a pause in deposition or erosion (sedimentary on bottom).
Half-Life
1 HL = 1:1, 2 HL = 1:3, 3 HL = 1:7, 4 HL = 1:15, 5 HL = 1:31
Earth’s Crust Composition
The most common elements in Earth’s crust are: silicon, oxygen, aluminum
Coal Formation
What is the principal source for the organic material in coal? Plants on land
Greenhouse Gases
Various greenhouse gases are carbon dioxide, methane, chlorofluorocarbon, ozone, nitrous oxide, and water vapor.
Earth’s Tilt and Seasons
What would happen if the tilt of our planet decreased to 21 degrees?
- Winters would get warmer, Summers would get colder
What would happen if the tilt of our planet increased to 25 degrees?
- Summers would get warmer, Winters would get colder
Climate Forcing
Positive forcing (results in more incoming energy or less outgoing energy) resulting in a warmer Earth; Example – melting of reflective sea ice, high wispy cirrus clouds
Negative forcing (results in more outgoing energy or less incoming energy) resulting in a cooler Earth; Example – volcanic eruptions where tephra creates dense clouds that block sunlight, thick cumulus clouds
Flood Basalts and Magma Plumes
Flood basalts are formed by magma plumes rising through the mantle from the core/mantle boundary.
Causes of Climate Change
Climate change may be due to:
- Natural external forcings → gradual changes in solar emission or changes in Earth’s orbit
- Natural internal processes of the climate system (more/less ice cover, volcanic eruptions)
- Anthropogenic forcings caused by humans (more greenhouse gases, air pollution)
Paleozoic Era
Check all the items below that occurred during the Paleozoic Era.
- – largest known extinction event in Earth’s history
- – major diversification of life in the oceans
- – evolution of amphibians and early reptiles
Atmospheric Composition
Nitrogen and oxygen make up 99% of dry air
Earth’s Albedo
The albedo of the Earth’s surface is highest at the poles. (surface: snow)
Radioactive Decay and Rock Dating
Radioactive decay determines the time of origin for igneous and metamorphic rocks only (not sedimentary!)
Oxygen Isotopes and Climate
The more O18, the cooler the period –> O16 releases as ice melts
Magma Viscosity and Volcanoes
The higher the silica content and lower the temp = the more viscous the magma will be
Low-density magma is more likely to produce shield volcanoes as high-density magma is more likely to produce composite volcanoes