Iridium is an extremely rare metal that is similar to platinum. Large concentrations of iridium are only found in meteorites (asteroids, meteors, or comets) that have crashed on Earth or after large volcanic eruptions that thrust the iridium out from deep within the Earth. Scientists concluded that a comet hit the Earth and wiped out the dinosaurs because of the concentration of iridium found in rock stratum from 65 million years ago. Which of the following, if true, most strongly supports the scientist's conclusion? A. Dinosaurs were not the only animals to die out 65 million years ago. B. A comet struck the Earth approximately \(28.5\) million years ago, but no widespread extinction resulted from that collision. C. A volcano large enough to generate high concentrations of iridium is extremely rare. D. Most scientists agree that a comet impact wiped out the dinosaurs.

Step by step solution

01

- Understand the Problem

The problem requires identifying the choice that most strongly supports the scientists' conclusion that a comet hit the Earth and caused the extinction of dinosaurs, based on the presence of iridium in rock strata.

02

- Evaluate Each Option

Analyze each given choice to determine which one best supports the hypothesis that a comet impact caused the extinction event 65 million years ago.

03

- Analyze Option A

Option A states that dinosaurs were not the only animals to die out 65 million years ago. This fact alone does not directly support the theory about the comet impact.

04

- Analyze Option B

Option B mentions that a comet struck the Earth 28.5 million years ago without causing a widespread extinction. This information does not support the hypothesis about the comet impact 65 million years ago either.

05

- Analyze Option C

Option C posits that a volcano large enough to generate high concentrations of iridium is extremely rare. This fact supports the conclusion by suggesting that it is less likely the iridium deposits came from volcanic activity, thereby supporting the comet impact theory.

06

- Analyze Option D

Option D states that most scientists agree that a comet impact wiped out the dinosaurs. While this indicates consensus, it does not provide direct evidence or support for the hypothesis.

07

- Select the Best Answer

Given the analyses, Option C most strongly supports the scientists' conclusion that a comet impact caused the extinction because it eliminates an alternative source of iridium.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Iridium Concentration

Iridium is a metal that is exceedingly rare on Earth but can be found in higher concentrations in certain cosmic objects like meteorites and comets. When scientists discovered layers of rock stratum from 65 million years ago that had unusually high levels of iridium, it led them to propose that an extraterrestrial object impact was responsible. Iridium's scarcity on Earth's surface makes its concentration in these ancient rocks an important clue.

• Rare on Earth's surface
• Common in meteorites and cosmic bodies
• High levels in rock strata point to an extraterrestrial origin

This keystone evidence suggests that whatever geological or extraterrestrial event occurred had to involve materials commonly found in outer space.

Rock Stratum

Rock stratum refers to layers of sedimentary rock that have been laid down over geological time. By examining these layers, or strata, scientists can decode the history of Earth's geological and biological changes. The presence of iridium in a specific layer of rock from approximately 65 million years ago marks a significant event.

• Layers show the chronological sequence of historical events
• Specific layer with high iridium levels marks 65 million years ago
• Helps date and correlate extinction events with geological data

Therefore, studying these layers allows scientists to pinpoint when significant changes or catastrophic events, like a comet impact, likely occurred.

Volcanic Eruptions

Volcanic eruptions can also release iridium, thrusting it from deep within Earth to its surface. However, such eruptions are rare and often limited in the extent of iridium they can release. For a volcano to account for the iridium concentration found in 65-million-year-old rock layers, it would need to be incredibly massive.

• Eruptions can bring deep-Earth materials to the surface
• Large-scale volcanic eruptions are rare
• Unlikely to account for the widespread iridium findings

Because mega-eruptions of this magnitude are rare, scientists give more weight to the hypothesis that a comet impact, rather than a volcanic source, explains the iridium.

Impact Events

Impact events involve cosmic bodies like comets or meteorites colliding with Earth, often creating craters and distributing materials like iridium over a wide area. The impact event hypothesized to have caused the dinosaur extinction involved such a collision approximately 65 million years ago.

• Extraterrestrial objects collide with Earth
• Can create shock waves and distribute rare elements
• Often leave a significant mark in geological records

This comet impact theory is supported by the widespread iridium found in the rock stratum from this period, strengthening the argument that such an event led to a mass extinction, including that of the dinosaurs.