Geo-Earth History

The major source of oxygen in Earth’s Early Proterozoic atmosphere is inferred to have been produced by

• oceanic cyanobacteria
• outgassing from volcanic eruptions
• radioactive decay in Earth’s inner core
• evaporation of ocean water

The diagram below represents three bedrock outcrops. The layers have not been overturned. Letters A through E identify different rock layers. Fossils found in the rock layers are shown.

• 1
• 2
• 3
• 4

Which geologic event occurred in New York State at approximately the same time as the extinction of dinosaurs and ammonoids?

• Formation of the Queenston Delta
• Deposition of the sands and clays underlying Long Island
• Initial opening of the Atlantic Ocean
• Advance and retreat of the last continental ice sheet

Volcanic ash deposits found in the geologic record are most useful in correlating the age of rock layers if the volcanic ash was distributed over a

• Large area during a short period of time
• Large area during a long period of time
• Small area during a short period of time
• Small area during a long period of time

The cross section represents four different rock units. The symbol for contact metamorphism is shown in the cross section.  What metamorphic rock will be formed in rock layer C?

• 1 Marble
• 2 Quartzite
• 3 Anthracite coal
• 4 Slate

The table below shows the radioactive decay of carbon-14. Part of the table has been left blank. After 22,800 years, approximately what percentage of the original carbon-14 remains?

• 15%
• 12.5%
• 6.25%
• 3.125%

Which event is generally accepted as the cause of the mass extinction that occurred 65.5 million years ago?Question*

• Volcanic eruption
• Continental collision
• Asteroid impact
• Sea-level change

The geologic cross section below includes an unconformity and an igneous intrusion.  Which two events produced the geologic unconformity in the rock record?

• Intrusion of magma, followed by contact metamorphism
• Intrusion of magma, followed by erosion of rock layers
• Erosion of rock layers, followed by deposition of more sediments
• Erosion of rock layers, followed by intrusion of magma

The timeline below represents time on Earth from the beginning of the Paleozoic Era (A) to the present (B). Which numbered position best represents the time when humans first appeared in the fossil record?

• 1
• 2
• 3
• 4

The cross sections below represent three outcrops, labeled I, II, and III, containing some New York State index fossils. The rock layers have not been overturned. When the rock layers in the three outcrops are correlated, the oldest layer is the

• Shale layer in outcrop I
• Siltstone layer in outcrop II
• Limestone layer in outcrop III
• Conglomerate layer in outcrop III