Geologic Times

Reviewer for Exam

Fossils

________- are the remains or traces of prehistoric life.

Angiosperms

________- flowering plants with covered seeds- replaced gymnosperms as the dominant land plants.

Carbonization

________ is particularly effective in preserving leaves and delicate animals.

Earth

________ is much older than anyone had previously imagined and that its surface and interior have been changed by the same geological processes that continue today.

Laurasia

________- is the continental mass that formed the northern portion of Pangaea, consisting of present- day North America and Eurasia.

Radioactivity

________- is the spontaneous decay of certain unstable atomic nuclei.

population of organism

○ It refers to the cumulative change in a(n) ________ over time.

columns of calcium

They are distinctively layered mounds or ________ carbonate.

Gymnosperms

________ are seed- bearing plants that do not depend on free- standing water for fertilization.

Trace fossils

________ are indirect evidence of prehistoric life.

Oxygen

________ began to accumulate in the atmosphere about 2.5 billion years ago.

Eons

________- represent the greatest expanses of time.

Uniformitarianism

________- the forces and processes that we observe today have been at work for a very long time.

Molds

________ and casts are another common type of fossil.

Correlation

________- is establishing the equivalence of rocks of similar age in different areas.

Mammals

________- animals that bear live young and maintain a steady body temperature- replaced reptiles as the dominant land animals in the Cenozoic era.

fine sediment

It occurs when an organism is buried under ________.

Shields

________ are large, relatively flat expanses of ancient metamorphic rock within the stable continental interior.

geological change

Revived Hutton's principle of slow ________, and presented a classic explanation of development over millions of years.

water dwelling

The elimination of a(n) ________ stage (like the tadpole stage in frogs) was an important evolutionary step.

Radiocarbon Dating

________- is the method for determining age by comparing the amount of carbon- 14 to the amount of carbon- 12 in a sample.

◆ Dinosaurs

________ were land- dwelling reptiles that thrived during the Mesozoic era.

Earths original atmosphere

________ was made up of gases similar to those released in volcanic eruptions today- water vapor, carbon dioxide, nitrogen, and several trace gases, but no oxygen.

Radiometric dating

________ has supported the ideas of James Hutton, Charles Darwin, and others who inferred that geologic time must be immense.

Law of superposition

________- states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it.

negative electrical charges

◆ Orbiting the nucleus are electrons, which are ________.

accurate radiometric date

A(n) ________ can be obtained only if the mineral remained in a closed system during the entire period since its formation.

angular unconformity

A(n) ________ indicates that during the pause in deposition, a period of deformation (folding or tilting) and erosion occurred.

radioactive isotope

Each ________ has been decaying at a constant rate since the formation of the rocks in which it occurs.

Inclusions

________ are rocks contained within other rocks.

Cenozoic era

◆ The ________ is divided into two periods of very unequal duration, the Tertiary period and the Quaternary period.

Half life

________- is the amount of time necessary for one- half of the nuclei in a sample to decay to a stable isotope.

geological events

Rocks record ________ and changing life forms of the past.

important components of sediment

They are ________ and sedimentary rocks.

gymnosperms

The ________ quickly became the dominant plants of the Mesozoic era.

Relative dating

tells us the sequence in which events occurred, not how long ago they occurred

Law of superposition

states that in an undeformed sequence of sedimentary rocks, each bed is older than the one above it and younger than the one below it

Principle of Original Horizontality

means that layers of sediment are generally deposited in a horizontal position

Principle of Cross-Cutting Relationships

states that when a fault cuts through rock layers, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger than the rocks affected

Correlation

is establishing the equivalence of rocks of similar age in different areas

Fossils

are the remains or traces of prehistoric life

Unaltered Remains

Some remains of organisms-such as teeth, bones, and shells-may not have been altered, or may have changed hardly at all over time

Two conditions are important for preservation

rapid burial and the possession of hard parts

The principle of fossil succession

states that fossil organisms succeed one another in a definite and determinable order

Index Fossils

are widespread geographically, are limited to a short span of geologic time, and occur in large numbers

Interpreting Environments

Fossils can also be used to interpret and describe ancient environments

Radioactivity

is the spontaneous decay of certain unstable atomic nuclei

Half-life

is the amount of time necessary for one-half of the nuclei in a sample to decay to a stable isotope

Radiocarbon Dating

is the method for determining age by comparing the amount of carbon-14 to the amount of carbon-12 in a sample

◆ There are three eras within the Phanerozoic eon

the Paleozoic, which means "ancient life," the Mesozoic, which means "middle life," and the Cenozoic, which means "recent life."

Stromatolites

The most common fossils

Following the long Precambrian, the most recent 540 million years of Earths history are divided into three eras

Paleozoic, Mesozoic, and Cenozoic

Laurasia

is the continental mass that formed the northern portion of Pangaea, consisting of present-day North America and Eurasia

Angiosperms

flowering plants with covered seeds-replaced gymnosperms as the dominant land plants