Abundance of a fossil: The amount of fossils of the same kind in a given area.

Accretion in stromatolite growth: The gradual growth of stromatolites by the layering of sand and bacterial communities.

Archaeocyathid: Early animals thought to have been related to modern sponges, though scientists are still unsure of their exact relationships to modern groups. Archaeocyathids were vase- or bowl-shaped organisms that pumped water through their porous walls to get food.

Assemblage: A group of fossils from similar time periods found in the same area.

Atmosphere: The layer of gases that surrounds the Earth.

Bacteria - Prokaryotic, unicellular, and usually microscopic organisms.

Bauplan a term which in German literally means Ôbody planÕ and is used to refer to the different major types of bodies that animals have, such as four legged creatures (tetrapods).  

Benthic A term used to refer to organisms that live on the bottom of the ocean or of a lake.

Bilateria - Animals with one line of symmetry in their body structure, such as humans, insects, flatworms, and many other types of animals.

Biomarkers fossilized lipids, or fat molecules, that are preserved in sedimentary rocks and can give us information on what types of organisms lives in ancient oceans.

Cambrian The earliest period of the Paleozoic era, when complex organisms became common. The Cambrian Explosion refers to the relatively quick diversification of life at the beginning of this period. The Cambrian lasted from 542 million years ago (Ma) to 488 Ma.

Clade A group of organisms with just one common ancestor.

Cap rock/Cap Carbonate: Layer of carbonate rock (like a limestone) that marks the end of the global ice ages.

Clast: Fragment of broken up rock.

Cross-bedding/Cross-lamination: The slanted and discontinuous patterns of sedimentary layers resulting from unevenly deposited sediment by wind or water.

Cryogenian: The time period in Earth history that spans the two major ÔSnowball EarthÕ  global glacial events, from approximately 850 million years ago (Ma) to 635 Ma.

Cyanobacteria: Bacteria that can perform photosynthesis.

Diamictite: A rock made up of many smaller chunks of poorly sorted clasts (or fragments of pre-existing rock).

Divots: Pieces of unearthed material.

Dolomite: A sedimentary carbonate rock that contains a lot of magnesium.

Drop stones Rocks that are isolated in a sedimentary rock by dropping down through a column of water during the formation of the sedimentary rock. Drop stones are often caused by rocks falling from the underside of melting glaciers into underlying sediment.

Ecospace The capacity or ability of an ecosystem to expand and diversify life.

Ediacaran The final period in the Neoproterozoic Era, lasting from 635 Ma to 542 Ma.

Ejecta Fragments or particles of rock that originated in a volcanic eruption.

Elephant Skin: A wrinkled texture in sedimentary rocks caused by the activity of microbial mats that formed in the original sediments.

Erratics: Rocks that have been transported, often great distances, by glacial ice and do not match the surrounding rocks.

Evaporite A mineral found in a sedimentary rock consisting mainly of salt formed by the evaporation of ocean water.

Feldspar: A group of minerals that contain aluminum and silicon, in addition to potassium, calcium, or sodium. Over 50^% of the earthÕs crust is made of feldspar minerals.

Frond: A bisymmetrical shape (two sides that are mirror images) similar to a palm leaf.

Geopetal: An indication in the layers surrounding a rock of the orientation of the rock when it was originally deposited.

Glaciation: The process in which parts of the Earth are covered in large bodies of ice.

Golden Spike: An internationally agreed upon point in rock that defines the beginning of a new geological period.

Grazers: Animals that feed off of algae and bacteria on rocks and on stromatolites.

Hematite: An iron mineral capable of preserving a magnetic field; scientists can use these magnetic fields to determine the approximate placement of a continent when a hematite rock was first deposited.

Holdfast: An organ that anchors an organism to the sea floor.

Hummock: A lump or mound.

Lineation: The structure of lines on a rock.

Lithification: The process by which loose sediments are compressed together to form rock.

Medusoid: Umbrella-shaped organism or jellyfish.

Microbial mat: A sticky layer of bacteria that forms a layer on the surface (can be under water or on land).

Multicellular: A description of an organism as being made up of more than one cell; these cells are often specialized to perform different functions in the organismÕs survival; animals, fungi, and plants are multicellular.

Neoproterozoic-- Geologic time period lasting from 1 billion years ago to 542 million years ago.

Organic matter: Carbon-rich material that was at one point part of a living organism.

Phanerozoic Eon describing the time period during Earth history during which diverse animals have existed, lasting from 542 Ma to the present.

Photosynthesis: The process by which organisms such as plants and cyanobacteria use energy from sunlight, water, and CO₂ from the atmosphere to make carbohydrates (food) and oxygen.

Plate Tectonics: The EarthÕs crust is divided into about 12 plates that fit together like a puzzle to form the outside of the Earth. These plates move in relation to one another, forming major surface features (such as mountains, volcanoes, oceanic trenches, and faults). 

Pores: Small openings that let water in and out.

Precambrian A term used to describe the time before the Phanerozoic, from the formation of the earth until 542 Ma.  

Protist A eukaryotic microorganism, such as an amoeba.

Precipitation in stromatolite growth: Cyanobacteria change the composition of the water around them, causing ions in the water to precipitate and form solid minerals.

Proliferation: A rapid increase in numbers.

Radiometric dating A technique geologists use to date rocks and fossils by comparing the natural abundance of a radioactive (atoms having unstable nuclei) isotopes (parent) and the abundance of the decayed product (daughter) in the rocks.

Rhythmite: A sedimentary rock formation of many small, even layers that are formed by rhythmic or periodic tidal or glacial processes, where very little sediment is deposited at a time.

Ripples (ripple marks): A series of ridges in sediment (usually sand) formed by the action waves and tides in shallow water; ripples are preserved in the fossil record and can be used by scientists to determine ancient environments.

Sandstone: Sedimentary rock made up of particles of sand.

Septae: Partitions or walls in a skeleton that divide an organismÕs body; usually refers to sponges and corals.

Shale: A sedimentary rock made up of extremely small particles of mud; shale is ÒfissileÓ and breaks into to thin layers that are parallel to the bedding.

Shoal: When sediment stacks up in one area of an ocean or river floor, that area becomes more elevated than another; these areas are characterized by very shallow water.

Silt: A granular material of a size between sand and clay.

Snowball Earth A hypothesis that at certain points in time the Earth was almost entirely frozen and covered with ice at the surface

Spicule: Tiny structures that stiffen the bodies of sponges, often made of silica.

Sponge: A marine animal in the Phylum Porifera that receives oxygen and food by pumping water through its porous body.

Stratigraphy The study of rock layers.

Stromatolite: Layered sedimentary structures built by bacterial communities and the accretion or precipitation of minerals. 

Suspension feeder: A marine organism that pulls in water and filters small particles of food from it. Examples include sponges and corals.

Taphonomy The study of decaying life; the science of looking at how organisms decay and fossilize.

Taxonomy The classification of living organisms.

Tidal flat: A low-lying area, often muddy, that is under water during high tide and exposed during low time.

Tillite: A type of diamictite formed by melting glacial ice; tillite is composed of poorly sorted (many different sizes and types of) rock fragments or clasts mixed together in a fine-grained matrix.

Uplift: The increase in elevation of areas of the EarthÕs surface in response to plate tectonics, erosion of material from mountain ranges, or the melting of glacial ice sheets. Uplift is one of the ways that sedimentary layers are exposed on the EarthÕs surface, allowing paleontologists to explore ancient life.

Volcanic debris: Ash and other particles released from a volcano.

Water column: The area between the surface of the water and the ocean floor.

Weathering: The breakdown of rocks and minerals resulting from mechanical, chemical and biological processes.