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Time Clues in a Desert Basin

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Time Clues in a Desert Basin

Use desert records to compare how long Earth changes take.

Read the Desert Records

Read the passage. Use its time clues to answer the questions. Choose one answer unless the question says otherwise.

The Basin Watch Station

At a desert basin, a science team studies changes in the land. The team uses cameras, old photographs, and field books. No one stands near falling rocks or rushing water. Cameras record those events from a safe place.

Rockfall record: A camera shows a large rock breaking loose from a steep slope. The rock falls, breaks into pieces, and stops moving within a few seconds.

Flood record: After heavy rain, muddy water rushes through a dry channel. It carries sand and small stones away. This flood lasts about twenty minutes.

Wind record: Wind blows sand against a sandstone rock. Tiny grains wear off its surface. Old photographs and field notes show that the rock's shape has changed a little over many years.

Canyon record: A field book describes the basin's deep canyon. Water has carried away rock and sand during many floods over thousands of years. The canyon did not reach its present depth during just one flood. The team compares these records to learn about Earth's changing surface.

1.
Which recorded change took the least time?
Question 1 options
2.
Sort the changes by how long they took in the records.
3.
Nia says, "One flood must have made the whole deep canyon." Which evidence best shows why she should change her idea?
Question 3 options
4.
Select the TWO observations that are evidence of very slow land changes.

5.
The flood lasted longer than the rockfall. Does that make this flood a very slow Earth event?
Question 5 options
6.
Each time windblown sand hits the sandstone, only tiny grains may wear off. How can the rock's shape change over many years?
Question 6 options

Check the Team's Evidence

Use the passage and the new camera notes. Think about what each record can and cannot show.

New camera notes
Slope camera: At 9:00, a large rock was on the slope. At 9:01, its broken pieces were at the bottom.
Sandstone camera: Photographs taken one day apart showed no change that the team could see.
7.
The sandstone looks the same in photographs taken one day apart. What is the best conclusion?
Question 7 options
8.
What can the two slope photographs show about the rockfall?
Question 8 options
9.
Which plan would best help the team check for more slow wear on the sandstone rock?
Question 9 options
10.
Omar says, "A large rock must take many years to fall because it is big." Which record best checks his idea?
Question 10 options
11.
The team will record another flood. Select the TWO notes needed to find out how long that flood lasts.

12.
Which statement goes beyond what these desert records show?
Question 12 options
13.
Does Earth's surface always change at the same speed? Use one quick change and one very slow change from the passage to explain. Include a time clue for each.