Earth Science Semester 2 Study Guide
Earth’s History
Chapter 30.1- Geologic Time
KEY VOCABULARY
• geologic time scale
• eon
• era
• period
• epoch
Summary
The geologic time scale summarizes the major events of Earth’s history as revealed in the rock record.
Changes over the past 3.8 billion years include the formation of Earth’s crust, the appearance and
disappearance of landforms, atmospheric changes, and the appearance and evolution of life forms.
Natural selection accounts for changes in species. The geologic time scale, based on the rock record,
summarizes major events in Earth’s history. The geologic time scale is divided into eons, eras, periods,
and epochs.
Be able to
Explain how the geologic time scale summarizes Earth’s history.
Explain the events that distinguish one time division from another.
Describe the 5 mass extinctions
Chapter 29 all sections
Key Vocabulary
• paleontology
• mold
• cast
• trace fossil
• relative dating
• strata
• unconformity
• correlation
• index fossils
• key bed
• absolute time
• varve
• radioactive decay
• parent isotope
• daughter isotope
• half-life
• radiometric dating
Summary



29.1 Fossils, evidence of earlier life preserved in rock, are the basis for the geologic time scale
and are an important part of the rock record. Fossils may occur as original remains, replaced
remains, molds and casts, trace fossils, and carbonaceous films.
29.2 Relative dating is used to place past events in order without determining actual dates
during which events occurred. Relative dating is also used to determine relative ages of
specimens such as rocks or fossils. Relative dating is based on the principle of superposition and
the principle of cross-cutting relationships. A gap in relative time may be the result of an
unconformity in the rock record.
29.3 Absolute time identifies actual dates of events or actual ages of specimens. Scientists use
radioactive-dating methods to measure absolute time. Radiometric dating relies on radioactive
decay and half-lives of elements such as carbon, uranium, rubidium, and potassium.
Be able to
Describe how fossils form
Summarize the principles scientist use to determine the relative age of Earth’s rocks.
Identify methods scientist use to correlate rock layers.
Explain the process of radioactive decay.
Define half-life
Describe how radiomentric dating is used to measure absolute time
Energy Resources Chapter 7 All sections
Key Terms
nonrenewable resource
fossil fuel
renewable resource
ore mineral
Summaries
 7.1 Earth’s environment includes all the renewable and nonrenewable resources, influences,
and conditions at Earth’s surface. Renewable resources are replaced by nature at a rate close to
their rate of use. Nonrenewable resources, which include minerals, exist in fixed amounts. A


resource can be exhausted if the demand for and use of it is greater than the amount that exists
in nature.
7.2 Humans use a variety of renewable and nonrenewable energy resources to meet their
energy needs. Nonrenewable energy resources include uranium and fossil fuels such as coal,
petroleum, and natural gas. Water, wind, the sun, and geothermal energy are types of
renewable energy sources.
7.3 The recovery and use of resources affects both the living and nonliving parts of the
environment. Mining minerals and rocks can harm soil, water, and living organisms.
Nonrenewable resources are limited and their use can cause pollution. Renewable energy
sources use no fuel and do not pollute but can be more expensive to use than fossil fuels.
Conservation, recycling, and environmental legislation can help protect resources and the
environment.
Chapter 13- Hydrogeology
Sections 13.1 & 13.2
Key Terms
tributary
river system
drainage basin
watershed
divide
gradient
discharge
deposition
pothole
load
suspension
bed load
competence
capacity
delta
Summaries
 13.1 A river system consists of a river and all of its tributaries. The drainage basin of a river
system is all the land that is drained by the river and its tributaries. A river’s velocity, gradient,
discharge, and channel shape affect how it erodes materials.
 13.2 Rivers wear down Earth’s surface and erode and deposit materials. A river may carry
materials in solution, in suspension, and in its bed load. Velocity and discharge affect how much
material a river can transport.
Be able to
 Describe the components of a watershed and river system
 Describe the characteristics of a river or stream that effect it’s ability to erode sediment- think
about the changes made in the stream table lab.
 Describe how streams transport and deposit sediment
 Explain how a delta forms
 Describe how streams erode the Earth’s surface.