Magma Dynamics & Volcanology
Geologists analyze these three primary factors to determine if a volcanic eruption will be violent or relatively quiescent.
What are composition, temperature, and dissolved gas content?
This fundamental concept states that the physical laws governing geology today have remained constant throughout Earth's history.
What is uniformitarianism?
This is the scientific consensus for the current age of the Earth.
What is 4.5 billion years?
When a glacier's accumulation exactly equals its wastage, the terminus of the glacier will exhibit this behavior.
What is being stationary?
This term refers to the general pattern of weather variations at a location over a long period of time.
What is climate?
This magma property increases as the percentage of silica in the melt rises.
What is viscosity?
According to this law, in an undeformed sequence of sedimentary rocks, each bed is older than the one above it.
What is the Law of Superposition?
Occurring at the end of the Paleozoic, this event represents the largest mass extinction in the Phanerozoic.
What is the Permian extinction?
Between sea ice and glacial ice, this type is typically thinner and originates from freezing ocean water rather than snow.
What is sea ice?
This is the primary energy source driving surface ocean currents like the Gulf Stream.
What is climate?
Of all the magma types erupted on Earth, this one is the most abundant.
What is basaltic magma?
This general term describes a buried erosional surface where rock layers are missing from the geologic record.
What is unconformity?
Identified in rocks nearly 3.5 billion years old, these are considered the earliest life forms on Earth.
What are prokaryotes?
Variations in Earth's orbit, known by this name, are considered the most likely cause of the Quaternary Ice Ages.
What are Milankovitch cycles?
This deep-ocean circulation is driven by differences in water density caused by variations in temperature and salinity.
What is thermohaline circulation?
This "winning" combination of magma traits is most likely to produce a highly explosive eruption.
What is high viscosity and high dissolved gas content?
To be classified as this, an organism must have lived for only a short period of geologic time but be geographically widespread.
What is an index fossil?
Scientists attribute the major source of free oxygen in our atmosphere to this biological group.
What are green plants?
This type of topography is characterized by sinkholes and is most commonly associated with areas underlain by limestone.
What is karst topography?
Occurring in the troposphere, this heat transfer mechanism involves the mass movement or circulation of a substance.
What is convection?
These are the two most abundant gases emitted specifically during basaltic volcanism.
What are water and carbon dioxide?
If a rock sample has undergone exactly two half-lives of radioactive decay, this is the percentage of the original parent material remaining.
What is 25 percent?
Some organisms utilize this specific greenhouse gas, for which the modern oceans are a major repository, to construct their shells.
What is CO2 (Carbon Dioxide)?
In a major river system, the gradient (slope) of the channel typically does this as you move downstream.
This atmospheric gas is vital for life because it filters out most of the ultraviolet radiation from the sun.
What is ozone?