The relative age of rocks

What is an index fossil?

A fossil that occurs at a specific time in history and allows us to date the earth where it was pulled from.

fault

(geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other

unconformity

A break in the geologic record created when rock layers are eroded or when sediment is not deposited for a long period of time

extrusion

An igneous rock layer formed when lava flows onto Earth's surface and hardens

intrusion

An igneous rock layer formed when magma hardens beneath Earth's surface

inclusion

Any piece of rock (clast) has become incorporated into another rock, this clast must be older than rock matrix it is included ini

Compare and contrast extrusion and intrusions

Extrusion are the lava that hardens on the surface Intrusion is when magma cools and hardens into a mass of igneosus rock

In your own words, define the terms relative and absolute age

He/she must be given at least a notice of the rule violation, a fair hearing and an opportunity to present his/her version of the issue

An intrusion crosses an extrusion. Which layer is older?

Intrusion is the oldest layer because it explains how lava goes to the bottom of the layers to harden.

relative age

The age of a rock compared to the ages of rock layers

Beside the law of superpositon, what are three types of clues to the relative age of rock layers.

The extrusion and the intrusion, and the fault explains the ages of rock layers .

What is the law of superposition

The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.

law of superposition

The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.

A geologist finds a cliff where the edges of serveral different rock layer can be seen. Which layer is the oldest?

The layer at the bottom of the rock layers is the oldest because over time dust and dirt build up from the bottom up.

index fossil

a fossil known to have lived in a particular geologic age that can be used to date the rock layer in which it is found

The fossil record shows that horsehoe crabs have existed with very little change for about 200 million years. would horseshoe crabs be useful as an index fossil? explains

modern organisms have unicellular ancestors, fossils occur in a particular order, most organisms that ever lived on earth are now extinct

Absolute age

the age of a rock given as the number of years since the rock formed