Vocabulary
The age of a rock is compared to the ages of other rocks.
relative age
Which term describes a gap in the geologic record that occurs when sedimentary rocks cover an eroded surface?
unconformity
Into which units is the geologic time scale subdivided?
Eras and periods
Which events occurred in the Cenozoic era?
Spread of mammals.
How many stomachs does a cow have
4
The age of a rock is given as the number of years since the rock formed.
absolute age
Which term describes the time it takes for half of a radioactive element's atoms to decay?
half-life
Rock layers and index fossils
What were Earth's earliest multicellular organisms
Invertebrates
This tall, cylindrical structure is used to store silage (fermented, high-moisture stored fodder).
Silo.
The preserved remains or traces of an organism that lived in the past.
fossil
Which statements best describe one rule for determining the relative age of a rock layer?
A fault is always younger than the rock it cuts through
How do geologists use radioactive dating in developing the geologic time scale?
To determine the absolute age of rocks.
The first birds evolved during the __________ era
Mesozoic
This is the term for a young female horse that has not yet reached maturity (usually under 4 years old).
Filly
The process in which the nuclei of radioactive elements break down, releasing fast-moving particles and energy.
radioactive decay
A geologist finds an area of undisturbed sedimentary rock. The..................... layer is most likely the oldest.
bottom layer
The geological time scale is a record of .................... and ...................
geologic events and life forms.
What was the earliest era of Earth's history
The Precambrian Time was the earliest part of Earth's history.
This process, usually done once a year, involves removing the thick wool coat from a sheep.
Shearing.
The geological principle states that in horizontal layers of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.
law of superposition
Which of the following conclusions can geologists draw about a limestone rock layer based on the law of superposition?
The limestone layer is younger than the sandstone layer below it.
Why do geologists need the geologic time scale?
1. Geologists use the geologic time scale to organize Earth's history.
2. It helps them determine when major geological events and different life forms existed on Earth.
In which era did mammals spread across Earth?
The Mesozoic Era during the Cenozoic Era.
While most people use the word "herd," this specific collective noun is also used to describe a group of goats.
Tribe.