Earth Science Midterm 2 Review
There are two different types of basaltic lava
Pahoehoe: Smooth ropy lava, flows easily.
AA: Sharp, jagged and slow moving.
Mt St Helens: When it was preparing to erupt, a giant buldge formed on the north flank.
This buldge is was a build-up of magma. When it erupted, smoke, gas, rocks and magama
exploded out of it. It formed a giant crater on top of the volcano. Flights were cancelled,
property and life around the volcano was destroyed and the people living near it were
evacuated. Now St Helens is a mountain with a giant crater on top and a mini mountain in
the middle of the crater.
Pyroclastic eruptions: Pyroclastic flows are deadly, fast moving clouds of volcanic ash
GIS: Any tool that’s used to measure/analyze something about earth.
Canadian invention 1963 Robert Thomasin. Started on desktop, now web based. Some
place to another (google maps), is a small part of GIS. There are 3D GIS now.
Used in many sectors.
Used with petroleum exploration. Can map surface and subsurface data. Able to propose
new fault zones that may contribute to reservoir generation.
Plate wizard: Allows us to reconstruct the positions of Earth’s plates. Allows
reconstructions at any time intervals (Cenozoic, Mesozoic).
Insurance companies use data to map areas who are at risk for floods and if one happens,
they will have an idea on how much they should reimburse.
The job market is huge, especially if you major in something and minor in GIS.
Cross cutting: Principle that an intrusion or fault is younger than the rock that it cuts
through or intrudes.
Superposition: A principle/law stating that within a sequence of undisturbed sedimentary
rocks, the oldest layers are on the bottom and the youngest on top.
Original horizontally: The deposition of most water-laid sediment in horizontal or near-
horizontal layers that are essentially parallel to the Earth’s surface. Unconformity: A surface that represents a break in the geological record, with the rock
unit immediately above it being considerably younger than the rock beneath it.
Layers have not been deposited continuously over time.
Disconformity: Sedimentary rocks above or below are parallel
Angular conformity: Folded, uplifted, eroded
Nonconformity: Metamorphic rocks underneath sedimentary strata.
Strategic: You can examine basic physical characteristics (observe lateral continuities).
Eg. Sandstone between shale above and conglomerate below.
Index: You can observe index fossils. Index fossils are short lived and evolve rapidly so
rocks containing the same fossils are the same age.
Radioactive decay: The spontaneous nuclear disintegration of certain isotope.
Geological time scale: A world wide relative scale of geologic time divisions. Weathering: The group of processes that change rock all or near the earth’s surface.
Erosion: The physical removal of rocks by an agent such as running water, glacial ice or
Rock cycle: Relating tectonism, erosion and various rock forming processes to common
rock types. Mechanical weathering: Physical process which disintegrates a rock without chemical
change. Increases surface are