Earth Science Review
The Earth and Solar System
Chemically, the Moon is quite similar to Earth’s mantle.
Most Common Elements in the Earth
The most common elements in the Earth as a whole are iron and oxygen.
Age of the Solar System
The age of the solar system is estimated by radiometric dates measured from meteorites.
Plate Boundaries
You are planning a study along a transect, mapping the geologic features between two points. You would almost certainly not find a transform plate boundary.
Mid-Ocean Ridges
The mid-ocean ridges are elevated above the surrounding sea floor because ridge rocks are warm and therefore of relatively low density.
Mineral Classification
Minerals are classified into groups known as mineral classes primarily on the basis of chemistry, specifically the anions within the chemical formula.
Igneous Rocks and Processes
Rock Identification
Based on its characteristics, the rock pictured would be called granite.
Intrusive Igneous Bodies
In the picture, a layer of mafic igneous rock is located between layers of shale and coal. Since we observe evidence of heating of the sediments on both top and bottom, the igneous layer should be called a sill.
Volcanic Rocks
- A rock composed of fragments of volcanic ash cemented together is called tuff.
- The Hawaiian mountain range is the product of magmas generated over a mantle hot-spot.
- Solidification of large or multiple magma chambers within continental crust forms igneous bodies called batholiths.
Magma and Cooling Rates
- When rock is partially melted, the chemical composition of the melt is more felsic than the original rock.
- Factors controlling the cooling rate of magma include: depth of intrusion, presence of circulating groundwater, and size and shape of a magma body.
Igneous Rock Textures
- As compared to coarse-grained igneous rocks, most fine-grained igneous rocks cool and solidify more quickly.
- A lava with the components to crystallize into olivine, pyroxene, and Ca-plagioclase is probably going to be fluid.
- The texture of the rock pictured can be described as scoriaceous.
- Pillow basalts attain their distinctive blob-like shapes because their parent lavas erupt underwater and thus cool very quickly.
Volcano Types and Hazards
- Of the major forms of subaerial volcanoes, strato-volcanoes consist of alternating layers of tephra and solidified lava.
- Several large volcanic eruptions have affected Earth’s climate, but heating that alters oceanic currents has not been observed.
- A complex dome that erupted and grew intermittently in the crater of Mt. St. Helens is made mostly of rhyolite and dacite rock.
- Around a shield volcano, the most significant volcanic hazard is lava flows.
- Lahars present the greatest hazard to people and structures in valleys around snow-covered stratovolcanoes.
- Andesitic volcanoes generally cause more explosive eruptions than basaltic volcanoes because andesite comes from more viscous magma.
- Yellowstone and Crater Lake are both the products of caldera eruptions.
Weathering and Sedimentary Rocks
Weathering Processes
- Large joints parallel to the land surface in granite outcrops are formed mainly by exfoliation.
- Colder average climatic temperatures would tend to produce slower rates of chemical weathering.
- The two minerals that usually remain after intense weathering of silicate rocks are clay and quartz.
- An example of a chemical weathering agent is the breakdown of calcite in rainwater.
- The chief origin of the salts that have accumulated in the oceans is the chemical weathering of continental rocks.
- When minerals rust, they are undergoing oxidation.
- Physical weathering can speed up chemical weathering by producing fresh surfaces for chemical weathering to attack.
Sedimentary Rock Identification
- The rock pictured with rounded gravel can be called conglomerate.
- Based on the shell fossils seen in the picture, the most probable rock name for this specimen is limestone.
Sedimentary Environments and Processes
- A deposit of bituminous coal can be interpreted as coming from a fresh-water swamp environment.
- A deposit of halite and gypsum evaporites could be interpreted as having formed from the evaporation of seawater.
- A hard sandstone with nearly all the clasts being smoothed quartz grains of equal size can be described using any of the following terms except immature.
- Petroleum originates from the accumulation and decomposition of marine microorganisms.
- The deposition and preservation of sedimentary structures can help us interpret all the following conditions or processes except the absolute age of the rocks.
- When limestone becomes chemically altered so that half of the calcium atoms are replaced by magnesium, the resultant rock is termed dolostone.
- Distinct internal laminations that are inclined at an angle to the boundary of the main layers are called cross beds.