Uniformitarianism reflects the belief among geologists that the Earth remains uniform and unchanging through time.

The principle of superposition states that within a sequence of undisturbed sedimentary rocks, the layers get younger going from bottom to top.

The principle of crosscutting relationships states that a disrupted pattern is older than the cause of disruption.

The principle of original horizontality states that beds of sediment are nearly always deposited as nearly horizontal layers.

In an unconformity the contact represents a gap in the geologic record.

Under some circumstances, correlation between two regions can be made by assuming that similar rock types in the two regions formed at the same time.

An index fossil is a fossil from a very short-lived, geographically widespread species known to exist during a specific interval of geologic time.

Earth is between 1 and 2 billion years old.

Geologists use fossils in sedimentary rocks to assign their correct place in geologic history.

The Mesozoic Era precedes (is older than) the Paleozoic Era. True or False?

So far, the oldest mineral found on Earth is approximately 4.56 billion years old.

A formation is the process by which sedimentary rocks come into existence.

Isotopes of the same element have different numbers of neutrons.

The proportional amount of atoms that decay with time is only influenced by pressure and temperature.

Half life is the time it takes for a given amount of a radioactive isotope to decay to half its original amount.

Radon is an intermediate product of uranium-238 decay.

Isotopic dates from volcanic ash or lava flows layered between fossiliferous sedimentary rocks have been used to assign numerical ages to the geologic time scale.

Another term for cosmogenic isotope dating is 'surface exposure dating'.

An angular unconformity is an erosion surface of igneous or metamorphic rock.

The Earth is approximately _____ years old.

Our ability to assign an age to geological and archaeological materials is based on our ability to measure the relative abundance of radioactive ___ and their stable decay products.

The Era is the Age of Mammals.

The ended with the greatest mass extinction ever to occur on Earth.

The half-life of the carbon 14 isotope is 5730 years. If there were 4 billion atoms of C-14 in a particular organism at the time it died, how many atoms of C-14 would there be in the remains of that organism 11,460 years after it died?

Fossils are common in __.

1. If the absolute ages measured for a set of igneous, sedimentary and metamorphic rock samples were exactly the same, would the rocks be the same age?

2. Most of geologic history is based on relative time because:

3. The major divisions of geologic time (eras, periods, and epochs) span different lengths of times, even though they are all expressed in years because:

4. Why isn't the age of the Earth established by dating the rocks on the Earth?

5. What is the difference between relative time and absolute time?

6. Extinctions play a significant role in the geologic time scale because:

If a dike protrudes through several layers of rock, what can we conclude?

The principle that state most layers of sediment are deposited in a nearly horizontal orientation is __________.

If a sandstone in contact with a granite contains fragments of the granite, what can you infer?

What are era's divided into?

Paleozoic is an example of_________.

What is Pangaea?

Age of fish was during this era:

Which is the correct order for the 3 eras on geologic time scale. This order is from oldest to current.

Which hypothesis has the most evidence for the cause of the extinction event that ended the age of dinosaurs?

Which layer is an intrusion?

The picture is an example of what kind of dating?

Which layer is the youngest?

Rocks found on land are up to 3.8 billion years old, but those in the ocean are no more than 180 million years old. Using the information shown, during which era could the oldest parts of the ocean floor have formed?

Layer 2 is probably what kind of rock?

Which layer is the oldest?

What is the Cambrian explosion?

First spiders, scorpions, centipedes, early insects, vascular plants, jawed fish and large reefs appear.

First amphibians. Extensive radiation of fish, land plants. Many corals, brachiopods and echinoderms.

The ___________________ Era is also commonly called the Age of Dinosaurs.

Modern humans appear. Four major glaciations cause rapid shifts in ecological communities. Rise of civilization and agriculture. Extinction of large mammals in northern hemisphere.

The ___________________ era is commonly called "The Age of Mammals"

According to the law of superposition, which layer is the youngest?

Absolute dating measures _________________.

What is the oldest rock layer?

Why is the fossil record incomplete?

Which of the following statements about the fossil record is true?

Lava pits are excellent sources for recovering fossils.

In what order do these appear in the geologic record (oldest to youngest)?

If one billion atoms of a radioactive isotope endure two half lives, about how many of these parent atoms will be left unchanged?

Which term means "ancient life"?

What time units are eras subdivided into?

Which of the following represents the longest time period

Which mineral contains U-238?

4,500 million years is the half-life of which radioisotope?

Which period of geologic time is known for major glaciation throughout the period?

Which period of geologic time is named after the Roman word for "Wales" and is best known for a major sudden increase in biodiversity due to increased O₂ in the atmosphere?

Which period of geologic time experienced an increase in marine biodiversity, including the first vertebrates, first terrestrial plants and ended in the first of the 5 major extinction events due to glaciation followed by sudden warming?

Which period of geologic time had a high sea level, warm tropical climate, shallow seas, and an increase in plant diversity which lead to large deposits of coal?

Which geologic time period experienced the most severe extinction event, had an increase in biodiversity where the forerunners of mammals evolved and when 70% of the Earth was covered with water.

Which period of geologic time began and ended in a major extinction event and includes fossils of the first dinosaurs?

Which period of geologic time began and ended in a mass extinction, is known as the "Age of the Dinosaurs" and contains fossils of the first birds?

Which geologic time period begins and ends in a mass extinction event believed to be caused by a meteor that hit Earth near the coast of Mexico?

It there is a period of major glaciation (large cover of ice on Earth at both poles), you can expect that sea level was

If the Earth has a tropical climate you can expect the O₂ levels to be

If the Earth is experiencing major tectonic movement you can expect

If the Earth has major volcanic activity one could expect the Earth to have

The study of geologic time reveals that the Earth has undergone extreme fluctuations in all of it's spheres leading to