Examkin

Question

Difficulty: EasyIdentifying Core Claims and Hypotheses

### Origin of the Grand Canyon

Two geologists present opposing theories regarding how the Grand Canyon in Arizona was formed.

Geologist 1

The Grand Canyon was formed rapidly, over a period of just a few weeks, by a single catastrophic flooding event. Approximately 5,0005,000 years ago, a large prehistoric lake located northeast of the canyon suddenly breached its natural dam. The sudden release of billions of gallons of water cut through the soft sedimentary rock layers, carving the entire depth and width of the canyon in a very short period.

Geologist 2

The Grand Canyon was formed gradually over millions of years through steady, continuous erosion by the Colorado River. Beginning about 66 million years ago, the Colorado River began flowing through the region. As the surrounding Colorado Plateau was slowly uplifted by tectonic forces, the river steadily downcut into the bedrock. This slow process of water erosion, aided by wind and weathering, gradually shaped the canyon into its current form.

Based on the passage, Geologist 1 claims that the Grand Canyon was carved by which of the following processes?

  1. a single catastrophic flooding event over a very short periodAnswer
  2. B
    steady, continuous erosion by a river over millions of years
  3. C
    tectonic forces that directly split the bedrock apart
  4. D
    lava flows from volcanic eruptions that filled a pre-existing valley

Answer

a single catastrophic flooding event over a very short period
The correct option is correct because Geologist 1 explicitly states that the Grand Canyon was formed rapidly, over a period of just a few weeks, by a single catastrophic flooding event caused by a breached natural dam.

Step-by-Step Solution

1
Identify which geologist's claim is targeted by the question.
The question asks for the process proposed by Geologist 1.
This narrows down the section of the text that must be analyzed to retrieve the correct information.
2
Locate the key claims made by Geologist 1 in the passage.
Geologist 1 states that the canyon was formed 'rapidly, over a period of just a few weeks, by a single catastrophic flooding event.'
This step extracts the core hypothesis of Geologist 1 directly from the text.
3
Match Geologist 1's stated mechanism to the correct answer choice.
The option proposing a single catastrophic flooding event over a very short period matches Geologist 1's claim.
This step eliminates the incorrect options and confirms the correct response.

Key Concept

Identifying Core Claims and Hypotheses
Rate this question

Topics

Identifying Core Claims and Hypotheses

More questions from this topic