Glossary

A

Abyssal plain
An underwater plain found along the deep ocean floor, usually between 3000 and 6000 meters
Accretionary lapilli
Fragments of molten rock that accrete around smaller particles and solidify into spherical balls. Associated with volcanic and impact fallout.
Age
A unit of geologic time that represents millions of years.
Alamo breccia
A deposit comprised of carbonate rock fragments of varying sizes that was created when the Alamo meteor struck the ocean floor
Anoxic
Without oxygen
Archaeocyathid
A reef-building marine organism that lived within warm tropical waters along the ocean floor during the Cambrian period (about 525 million years ago)
Argonite
Needle-like mineral made of calcium carbonate (CaCO3); used to build shells by many marine invertebrates.

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B

Basalt
A common volcanic rock that is often grey to black and made up of small minerals due to rapid cooling of the lava on the surface of the Earth.
Bathymetry
Topography of the seafloor.
Benthic
Plants and animals that live on the sea floor.
Biogenic
Refers to sediment created by an organism.
Bolide
A large meteor.
Brachiopod
A two-shelled invertebrate animal with bilateral symmetry resembling a clam; has a particularly rich fossil record during the Devonian period.

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C

Calcareous
Made of calcium carbonate (CaCO3).
Calcite
Rhombus-shaped mineral made of calcium carbonate (CaCO3); most stable form of CaCO3).
Carbonate
A group of sedimentary rocks composed primarily of carbonate minerals (ex: limestones and dolomites)
Carbonate shelf
Marine carbonate rock depositional environment fringing a continent.
Cast
A three dimensional object made from filling of a mold.
Chordata
Phylum of organisms containing a spinal chord.
Clastic
Rocks made form detrital sediment.
Columnal
Disc-like components that make up crinoid stalks.
Conodont
An extinct eel-like creature known for its tooth-like microfossils known as conodont elements. The diversity and widespread occurance of conodonts throughout the Paleozoic Era make them an excellent fossil for biostratigraphy.
Continental rise
The underwater feature that lies between the continental slope and the abyssal plain, marking the transision into the deepest portion of the ocean
Continental shelf
An extended portion of each continent that lies underwater
Coralite
Domicile structure created by a coral polyp.
Craton
Old stable continental lithosphere.
Crinoid
Marine organisms that make up the class Crinoidea of echinoderms. Today they are often referred to as sea lilies because of their flower-like apearance. Several crinoid species still exist today

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D

Detrital
Sedimentary rock constituents that have come from a pre-existing rock; all clastic grains are detrital.
Diagenesis
Processes that happen to a rock, short of metamorphism, after deposition.
Diamond
A mineral comprised entirely of carbon and known for its high strength and optical properties.

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E

Ecospace
The space occupied by specific organisms in their respective ecosystems.
Ejecta
The debris ejected into the air during the formation of an impact crater.
Eon
A unit of geologic time that represents a half a billion years or more.
Epeiric sea
Broad shallow sea covering a large portion of a continent.
Epoch
A unit of geologic time that represents tens of millions of years.
Era
A unit of geologic time that represents several hundred million years.
Extant
Still in existance
Extensional force
A pulling-apart force that in geology often forms normal faults

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F

Facies
The character of a rock expressed by its formation, compostition, and fossil content.
Fault breccia
Breccia formed by tectonic forces.
Feldspar
A group of silica-based minerals that make up 60% of the crust.
Final apparent crater diameter (DA)
The distance from rim to rim of the cavity once collapse has completed.
Fossilization
The process by which a living organism becomes a fossil.

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G

Graben
An elongated block of the earth's crust lying between two faults and displaced downward relative to the blocks on either side
Grainstone
A grain-supported carbonate sedimentary rock that contains no mud; often they consist of skeletal grains.
Graphite
A weak mineral comprised entirely of carbon and known for its use in pencils (often called lead).
Gravity flow
Sediment flows that are produced when friction and/or cohesion of the particles is overcome, such as debris flows and turbidity currents.
Greenhouse
Times in the history of the Earth when there is little or no polar ice.

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H

Horst
A raised elongated block of the earth's crust laying between two faults
Hypersaline
Conditions of elevated salt content (salinity generally greater than about 40 ‰)

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I

In situ
Latin; describes a rock that formed In Place.
Indurated
Word used to describe sandstone that has been lithified.
Intraformational folds
Highly deformed layers of rock within non-deformed rock.

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J

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K

Karst
A geological formation shaped by the dissolution of carbonate rock, such as limestone or dolomite.

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L

Lithification
Process of creating a rock.

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M

Ma
Abbreviation or the term Millions of Years Ago.
Megaclast
A large, boulder-sized rock.
Mold
Impression left in sediment or rock by an organism.
Monomict
A rock whose fragments consist of one rock type.

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N

Nektonic
Free swimming organisms that spend the majority of their lives in the water column.
Niche
The ecological role played by a specific group of plants or animals.
Normal faults
A fault in which the hanging wall block has moved downward relative to the footwall block.
Normally graded
A bed of rock that is characterized by a decrease in grain size from bottom to top.

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O

Orogeny
Forces and events leading to structural deformation of the Earths lithosphere.

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P

Period
A unit of geologic time comprised of epochs and ages.
Planktonic
Plants and animals that live in the water column and do not have their own form of propulsion.
Polymict
A rock whose fragments consist of many types of rock.
Polyp
The filter feeding animal commonly known as corals and anemones.
Primary sedimentary structures
Large-scale features that form in sedimentary rocks during deposition.
Protozoan
Animals that rely on photosynthetic algae.
Proximal
Situated nearer to a point of reference. In terms of marine environments, a proximal environment lies closer to the shoreline

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Q

Quartz
The second-most abundant mineral on Earth whose crystalline structure is comprised of a framework of silicon-oxygen tetrahedral, SiO4.
Quartzite
A hard metamorphic rock that was originally sandstone.

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R

Reef talus
Rock composed of reef debris (such as coral and sponge remains) that is deposited along the downslope margin of an organic reef.
Replace
The growth of a mineral within another of different chemical composition by gradual simultaneous deposition and removal
Resurge waves
Waves travelling back towards the point of disturbance. During an impact within the ocean, waves are sent towards the shoreline and bounce back towards the impact site

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S

Sediment
Unconsolidated rocks and minerals.
Sedimentary rock
A type of rock composed of sediments from pre-existing rocks or organisms that have been eroded and deposited elsewhere.
Sedimentary structures
Features of sedimentary rocks that reflect something about the depositional environment.
Shelf break
The transition from the continental shelf to the continental slope, characterized by markedly increased slope gradients
Soluble
A substance that is able to be dissolved.
Steinkern
Fossil molds of the interior of invertebrates that form when sediment fills an empty shell and becomes lithified and remains even when the shell itself dissolves away.
Stishovite
An extremely hard, dense form of silicon dioxide (SiO2) created under high pressures (2-3 GPa) and high temperatures (~700°C).
Strata
Distinct layers of rock
Stromatolites
Layered structures created by microorganisms found in shallow water environments.
Stromatoporoid
Extinct marine invertebrates that formed calcareous layers and pillars, thought to be sponges, and were particularly abundant in the Devonian Period.
Supereon
The largest unit of geologic time that is made up of eons.

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T

Tectonic plates
Pieces of the Earths crust and uppermost mantle that move independent from one another.
Transient crater diameter (Dt)
The cavity formed immediately after the end of crater excavation, before it undergoes collapse and modification. Its outer extent is defined by the boundary between excavated and non-excavated target material.
Tsunami
A series of water waves caused by the displacement of a large volume of a body of water.

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U

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V

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W

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X

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Y

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Z

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