Unit 4 vocab Earth Science honors

absolute age rock

the numerical age of a rock or geological event, expressed in years, determined using methods like radiometric dating.

disconformity

unconformity between parallel layers of sedimentary rocks which represents a period of erosion or non-deposition

eon

longest period of time

epoch

smallest period of time

era (geological time)

2nd longest period of time

evolution

how animals and plants adapt over time.

fossil

A object of a prehistoric or living animal or plant.

geological column

an idealized, chronological diagram showing a sequence of rock layers stacked with the oldest at the bottom and the youngest at the top

half life

the time required for a quantity of a substance to reduce to half of its initial value through exponential decay

index fossil

the remains of a plant or animal that lived for a short period of geologic time but spread across a wide geographic area

law of cross cutting relationships

any geological feature that cuts across or disrupts a body of rock must be younger than the rock it intersects

law of faunal succesion

fossilized organisms succeed one another in a specific, reliable, and predictable order through geological time

law of intrusive relationships

any igneous intrusion is younger than the rock layers or pre-existing structures it cuts through

law superposition

in any undeformed sequence of sedimentary rock layers, the oldest layer is at the bottom and the youngest layer is at the top

mass extinction

a widespread and rapid drop in the biodiversity of Earth where at least 75% of species die out in a short geological time

nonconformity

a missing gap in the rock record caused by erosion or a long pause in sediment deposition before new layers form above

paleontology

study of fossils and the past.

period (geological time)

a standard unit of geologic time scale during which a specific system of rock layers was deposited

precambrian time

the earliest and longest span of geologic time

principal of original horizontality

layers of sediment are originally deposited in flat, horizontal or near-horizontal layers under the action of gravity

principle of uniformitarianism

the geologic processes shaping the Earth today have operated in the same way and with similar intensity over vast stretches of geological time

radiometric dating

Method used for absolute dating

relative age (rock)

Age of a rock or fossil based off fossils around it.

trace fossil

a geological record of biological activity and behavior rather than the preserved physical remains of an organism itself

unconformity

a break in time and continuity in the rock record caused by a period of erosion or a pause in sediment accumulation

varve

a pair of alternating sedimentary layers (a light/dark couplet) deposited in a body of still water, usually a lake, representing one exact year of accumulated sediment