The interval of geologic time between approximately 66 and 56 million years ago.
One of the four large divisions of geologic time, it includes six geologic periods, from 541 million to 252 million years ago.
Any aquatic mollusk belonging to the class Pelecypoda (phylum Mollusca), which includes clams, mussels, scallops, and oysters. Pelecypods have two symmetrical calcareous shells, called right and left valves, that are joined by a hinge. Pelecypods are also known as bivalves because of this bilateral symmetry. Most pelecypods are bottom-dwelling and live in shallow marine waters.
The interval of geologic time from 323 million to 299 million years ago. The period is named after the state of Pennsylvania in which rocks of this age are widespread and yield much coal. In Kansas, good exposures of Pennsylvanian rocks showing alternations of shale and limestone exist in many places in eastern Kansas.
A unit of geologic time. Several periods make up an era.
Permeability is a measure of the ease with which a fluid will move through a porous material (sand and gravel or rock, for example). A geologic unit is permeable if groundwater moves easily through it.
The interval of geologic time from approximately 299 million to 252 million years ago. In Kansas, rocks from the early part of the Permian include many of the limestones and shales that form the Flint Hills; later Permian deposits include the red beds of south-central Kansas.
The interval of geologic time between approximately 2.6 million and 11,700 years ago.
The interval of geologic time between approximately 5.3 million and 2.6 million years ago.
Geologically, this term describes rock that permits movement of fluids through small, often microscopic openings, much as water moving through a sponge. Porous rocks may contain gas, oil, or water.
The interval of geologic time before the Cambrian Period, from approximately 4.6 billion to 541 million years ago.
Water in some form that falls from the atmosphere. It can be in the form of liquid (rain or drizzle) or solid (snow, hail, sleet).