Earth & Space World

What is the stratigraphic layer

A stratigraphic layer is a layer of sedimentary rock formed during a certain time period. (colour, particle size, type of rock)

Sedementary rock

Sedimentary rocks contain layers of sediment that accumulate on top of each other. Under pressure, over a long period of time, the sediment accumulate forming sedimentary rock. These layers are called strata.

Relative dating:

Determining the approximate age of rocks by comparing their location in the stratigraphic layers

Absolute dating:

more accurately determining the age of rock or fossil by using methods such as carbon dating

Two types of relative fossil dating:

Law of original continuity and Law of superposition

Law of original continuity

fossils found in the same strateographic layer where formed during the same time period

Law of superposition:

older fossils are buried in the deeper stratigraphic layers than the more recent fossils.

Geological time scale

tool used to represent the major events that have occurred in the history of earth

Separation of geological time scale

The geological time scale separates the history of the Earth into 4 main divisions. Each division is marked by major events such as extinction or appearance of new life forms.

Geological time scale:

Cenozoic: quaternary, tertiary

Mesozoic: cretacious, jurassic, Triassic

Paleozoic: permian, carboniferous, devinian, silurian, ordovacien,cambrian

Pre cambrian:

Extinction:

disappearance of all individuals of a species. extinction is brought about by inability of the individual to adapt to changes in the environment

Mass extinction

Mass extinctions occur when many species disappear within a very short time frame due to a rapid change in the environment .

5 periods of mass extinction:

Cretacious, triassic, permian, devonian,ordovacien

Fossils:

any remain or trace of an organism that has been preserved for a very long period of time in the earth’s crust (sedementary rock)

4 types of fossils

• petrified fossils

• cast fossils

• True form fossils

• Trace fossils

Petrified fossils

remains of organism harden forming a rock-like material (bones and teeth)

Cast fossils

Remains of an organism decay and dissolve, leaving an impression of an organism in the rock (mould)

True form fossils (body)

formed when organism’s remains did not decay due to being trapped in some material that preserved the remains

Trace fossils

an imprint left in the soil is covered by sedements wich dries and hardens, conserving the trace. The sediment is then burried and compacted, eventually forming rock

why are fossils important in dating strateographic layers

If you know the age of a fossil, it can help you date the layer of rocks in which it is found. Stratigraphic layers allow the determination of a fossils relative age

favourable conditions for life to exist

• presence of a gaseous atmosphere

• presence of an energy source (Star)

• presence of water

Presence of a gaseous atmosphere

Elements such as carbon, oxygen, hydrogen and nitrogen makeup essential gases in the atmosphere. The atmosphere protects us from harmful radiation, and traps heat providing suitable temperature range (allowing for chemical reactions to take place)

Presence of a energy source (a star)

in order for more complex molecules to be formed, a large amount of energy is needed. Energy is required to drive the chemical reaction needed for the development of life. Ex; sun

Presence of liquid water

Planet must have lots of water because it is an ideal environment that allows complex molecules to bond and lead to the emergence of life. Water is also the primary constituent of all living organisms.

Time:

The more time that passes the more molecular bonds can be formed and this creates a greater probability of producing living cells and organism