Lecture 17: Relative Age and Geologic Maps

This set of flashcards will help students review important vocabulary terms and concepts from the lecture on relative age and geologic maps.

Geologic timescale

A system of chronological dating that relates geological strata to time.

Eon

The largest division of geological time, spanning hundreds to thousands of millions of years.

Era

A division of geological time that is smaller than an eon, typically lasting tens to hundreds of millions of years.

Period

Subdivisions of eras in the geologic timescale, lasting from millions to tens of millions of years.

Epoch

Subdivisions of periods that represent distinct stages in the geological history.

Law of Original Horizontality

The principle that layers of sediment are originally deposited horizontally.

Principle of Lateral Continuity

The idea that layers of sediment initially extend laterally in all directions until interrupted.

Law of Superposition

The concept that in a sequence of undeformed sedimentary rocks, the oldest layers are at the bottom.

Principle of Inclusions

The principle that fragments of rock included within another rock must be older than the rock they are included in.

Principle of Cross-Cutting Relations

The principle stating that geological features that cut across rocks must be younger than the rocks they cut through.

Intrusive Igneous Rocks

Rocks formed from magma that cools and solidifies within the crust of the Earth.

Batholith

A large igneous intrusion that forms from cooled magma deep within the Earth's crust.

Dike

A narrow, vertical sheet of magma that cuts through pre-existing rock layers.

Sill

A horizontal sheet of magma that intrudes between layers of sedimentary rock.

Unconformity

A surface representing a gap in the geological record, where rock layers were eroded or not deposited.