Week 8 (Unit 2) - Earth Science

Mass Wasting & Geochronology

What is Mass Wasting?

Earth materials moving downhill due to gravity.

What is the driving force of mass wasting?

Gravity.

What are the resisting forces?

• Friction

• Rock strength

• Gravity

What is rockfall?

Rock/Material falls through the air (may slide, bounce, or roll).

What is talus?

Rock debris at the bottom of steep slopes.

What is a slide?

Movement along a distinct failure surface.

Difference between Translational vs. Rotational slide?

• Translational = FLAT surface

• Rotational = CURVED surface

What is a CREEP?

VERY SLOW movement of soil downhill.

Difference between Relative vs. Numerical age?

Relative = What happened first

Numerical = How old something is

Difference between Catastrophism vs. Uniformitarianism?

Catastrophism = Sudden changes

Uniformitarianism = Gradual change over time

What is original horizontality?

Sediment layers are originally deposited mostly flat.

What is SUPERPOSITION?

Younger rocks = Top

Older rocks = Bottom

What is LATERAL CONTINUITY?

Rock layers continue SIDEWAYS (can be correlated)

What is CROSS-CUTTING?

Something cuts through another rock is younger.

What is a BAKED CONTACT?

Baked/Heated rock is older

What is the PRINCIPLE OF INCLUSIONS?

If ROCK A is inside ROCK B, ROCK A is older.

What is an UNCONFORMITY?

Missing time in the rock record

What are the 3 TYPES of unconformities?

1. Angular

2. Non-conformity

3. Disconformity

What is an ANGULAR unconformity?

Layers are angled.

What is a NON-CONFORMITY?

Non-Bedded (and Crystalline) rock underneath.

What is a DISCONFORMITY?

Layers are parallel but time is missing.

What is an ISOTOPE?

Atoms of the same element but with different numbers of neutrons.

What are the charges of the 3 particles?

• Proton = Positive

• Neutron = Neutral

• Electron = Negative

Difference between Stable & Unstable isotope?

Stable = Remains stable

Unstable = Unstable eventually decays

What is a PARENT isotope?

The ORIGINAL radioactive isotope.

What is a DAUGHTER isotope?

Product after decay

What is a HALF-LIFE?

Time it takes for HALF of the remaining parent atoms to decay.

How does RADIOACTIVE DECAY help date rocks?

The amount of parent/daughter isotopes tells us the rock’s age.

What happens to parent material as time passes?

Parent decreases, Daughter increases

Name other dating methods!

• Tree rings

• Ice Layers

• Varves

• Magento-Stratigraphy

• Fission Tracks

• Astronomy