Index Fossil Definition An Index fossil, in the field of paleontology, refers to a fossil that identifies and dates the stratigraphic unit that it is observed to exist in. Index fossils can combine a wide geographic range. And they can really narrow down the classifications of most stratigraphic units.

What is a Concrete Arch Dam? A Concrete Arch Dam is a curved freshwater-retaining structure that is concave in the hydro-geologically down-gradient direction, and uniformly thick from the base to top. With Concrete Arch Dams, a major part of the water load value gets distributed to the abutments of the dam. Thus, Concrete Arch Dams…

What is an Embankment Dam? An Embankment Dam is a freshwater-retaining structure comprising excavated rock, soil, or a combination of rock and soil from nearby geological formations.  In fact, Embankment Dams are known as an “Earthfill Dam” when filled with soil, and a “Rockfill Dam” when filled with rocks. Earthfill Dams are most common. The…

Natural Gas Natural Gas: In geology, natural gas means combustible hydrocarbon gas that forms by natural geological or biological processes. To illustrate, natural gas that forms by geological processes is the thermal decomposition of buried organic materials. Whereas natural gas that forms via biological processes entail the microbial decomposition of buried organic material. Natural gas…

Alquist-Priolo Earthquake Fault Zoning Act Alquist-Priolo Earthquake Fault Zoning Act: The Alquist-Priolo Earthquake Fault Zoning Act is a law that assists geologists to define “active faults” versus “potentially active faults.” The process entails using the same aging criteria as the United States Geological Survey (USGS) and the California Geological Survey (CGS). In fact, California policy requires…

Plutonic Rock (Igneous) Definition The term “Plutonic” in the field of geology refers to an igneous rock, wherein the magma had originally cooled, solidified, and crystalized underground. A plutonic rock is generally coarsely crystalline (phaneritic) and is formed during a massive geologic intrusion of magma. In fact, outcropping (or daylighting) plutonic rocks are geologic features…