Geologic Time

Which number best represents when humans are inferred to have first appeared on Earth?

• 1

• 2

• 3

• 4

Based on the graph, what is the approximate number of radioactive atoms of Isotope X that are present when 8 hours of decay have occurred?

• 50

• 100

• 155

• 200

Tags

NGSS.HS-PS1-8

Based on the graph, the half-life of this radioactive isotope is

• 6 hours

• 9 hours

• 3 hours

• 12 hours

Tags

NGSS.HS-PS1-8

The solid black sections of the bars on the graph represent the percentages of

• carbon-14 from the original sample that has not decayed

• uranium-238 from the original sample that has not decayed

• lead-206 decay product resulting from the radioactive decay

• carbon-14 decay product resulting from the radioactive decay

Tags

NGSS.HS-PS1-8

After 22,800 years, approximately what percentage of the original carbon-14 remains?

• 15%

• 6.25%

• 12.5%

• 3.125%

A fossil formed 11,400 years ago. Which percentage of the original amount of carbon-14 remains in the fossil?

• 100%

• 50%

• 25%

• 12.5%

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

Which sequence of geologic events is in the correct order, from oldest to most recent?

• oxygen begins to enter the atmosphere --> earliest stromatolites --> initial opening of the Atlantic Ocean --> extinction of the dinosaurs

• extinction of the dinosaurs --> initial opening of the Atlantic Ocean --> oxygen begins to enter the atmosphere --> earliest stromatolites

• initial opening of the Atlantic Ocean --> earliest stromatolites --> oxygen begins to enter the atmosphere --> extinction of the dinosaurs

• earliest stromatolites --> oxygen begins to enter the atmosphere --> initial opening of the Atlantic Ocean --> extinction of the dinosaurs

Tags

NGSS.MS-ESS1-4

NGSS.MS-ESS2-2

Which sequence best describes the geologic history, from oldest to youngest, that occurred at this site?

• F, D, C, B, E, A

• E, F, D, C, B, A

• F, D, C, B, A, E

• B, C, D, F, A, E

Tags

NGSS.MS-ESS1-4

NGSS.MS-ESS2-2

Which rock unit is the youngest?

• A

• B

• C

• D

Tags

NGSS.MS-ESS1-4