Unit 4 Exam Study Guide - Earth Science

In a conventional timeline, what is the largest period of history?

The Hadean period

What is the Law of Superposition (Relative)?

In an undisturbed sedimentary rocks, the oldest rock will always be on the bottom and the youngest rock on the top.

What is Cross-Cutting Relationships (Relative)?

The unit or fault which cuts across the strata is younger than the strata it cuts across

What is an unconformity?

A buried erosional surface

What is a disconformity?

An obvious erosional contact between two sedimentary rocks

What is an angular unconformity?

When sedimentary rocks below sit at an angle to sedimentary layers above

What is a nonconformity?

Sedimentary rocks that unconformable overlie igneous or sedimentary rocks

What is a paraconformity?

A supposed erosional surface or break in time (hiatus) that has no obvious reason

What are Inclusions (Relative)?

Older pieces of rock that get incorporated into newer deposits

What is the Order of Events?

Using the Law of Superposition and Cross-Cutting Relationships to determine the order of events

Biostratigraphy (Relative & Absolute)

Dating method based on various animals in certain layers of rock

What are some problems with Biostratigraphy dating?

1. It is dependent upon the assumption of biological evolution and faunal succession

2. It assumes that the earth is old and that certain suites of animals lived during certain periods of geologic time

3. Assumes if the fossils are the same, the rocks are the same age

What type of rock is the only one that can be dated Radioactively?

Igneous rocks

What are the 3 types of decay?

1. Alpha

2. Beta

3. Electron Capture

What is Alpha Decay?

When an unstable Parent nucleus ejects an alpha particle (Helium) to become a stable Daughter nucleus, producing energy in the process.

What is Beta Decay?

When a Neutron sheds a negative Beta particle to become a Proton, producing energy in the process.

What is Electron Capture?

When a Proton grabs an electron to become a Neutron, producing energy in the proces

What is half-life?

The amount of time that it takes for one half of the radioactive isotope to change into its daughter product. Can you draw a progression?

What is fission?

When the Parent isotope splits into two smaller daughter isotopes, often with the release of additional nuclear materials and energy. The two daughters explode out and travel in opposite directions, destroying some of the structure of the mineral.

According to the Conventional time model, what time period were trilobites alive?

Paleozoic

According to the Conventional time model, what time period were the dinosaurs alive?

Mesozoic

According to the Conventional time model, when were most mammals alive?

Cenozoic

Is the fossil record biased towards fragile or durable shells?

The record does not show bias

What time period did the Cambrian Explosion occurr in?

Paleozoic