geology 2.1 - 2.5

Rocks

Igneous: this rock forms from the cooling of magma that escapes to the Earth’s surface.

Sedimentary: this rock forms in layers packed down with pressure over long periods of time.

Metamorphic: this rock forms between the continental plates and is changed.

Nicolas Steno who created 2 laws

Relative age: the age of a rock or fossil compared to the ages of the layers around it, without giving an exact number of years.

Absolute age: the number of years that have elapsed since an event occurred.

The order of steps in the process of fossilization

Life —> death —> burial —> preservation —> discovery—> recovery

Difference between the 2 terms

Anaerobic: does not require oxygen

Aerobic: requires oxygen

Cambrian explosion and biggest mystery surrounding it

Oxygen levels reached a high enough concentration to support the more active metabolism of mobile organisms.

The short time it took at the variety of organisms found.

Superposition

A sequence of rocks is the chronological record of a given region.

Stratigraphic sequence

A sequence of rocks that is a chronological record of the region’s geological history.

Relative dating

The process of placing rocks and geological structures in the correct chronological order.

Intrusion

A body of rock that forms from the invasion of magma into pre-existing rock formation.

Stromatolites

Alberta’s earliest fossils

Mould/Imprint

Material has dissolved leaving an impression.

Trace fossil

No remains of actual organism but there is evidence of their presence.

Petrified

If the original material is replaced by a mineral (silica)

Cyanobacteria

The organisms responsible for producing much of original Earths atmospheric oxygen.

Index fossil

Can be used to correlate rock layers in different locations.

Trilobite

Earth: 4.6 billion years old

Universe: 13.5 billion years old

Burgess Shale

Organisms fossilized in it were once inhabiting a shallow area along the edge of a tropical sea (mount Walt’s in the Rockies full of preserved fossils)