Question

Scientists suggested the dinosaurs became extinct when an asteroid collided with Earth. They noted that the rare element iridium was present in 65-million-year-old rock layers around the world. The text in italic is an example of: a) A hypothesis b) A prediction c) An observation d) A theory

Short answer

d) A theory

Step-by-step solution

Identify the Context

The text refers to a historical scientific event where a theory was proposed to explain the extinction of the dinosaurs.

Analyze the Italicized Statement

The statement "Scientists suggested the dinosaurs became extinct when an asteroid collided with Earth" is a claim proposing a cause for the extinction event.

Determine the Nature of the Statement

The statement is a proposed explanation for a phenomenon based on available evidence, which aligns with the definition of a scientific theory.

Key concepts

Dinosaur Extinction

The extinction of dinosaurs is one of the most fascinating events in Earth's history. Approximately 65 million years ago, these gigantic, diverse creatures suddenly vanished from our planet. While the exact cause of their extinction remains a subject of much study and debate, many scientists believe that a dramatic environmental change led to this mass extinction. Factors that may have contributed include a drastic shift in climate, volcanic activity, and, most notably, an asteroid impact. Understanding dinosaur extinction helps scientists learn about Earth's past and how ecosystem changes can affect life on our planet.

Asteroid Impact

The idea of an asteroid impact as a catalyst for dinosaur extinction proposes that a large asteroid collided with Earth about 65 million years ago. The impact site is believed to be the Chicxulub crater located in the Yucatán Peninsula, Mexico. This catastrophic event would have generated massive amounts of energy, releasing dust and debris into the atmosphere. As a result, it blocked sunlight, leading to a significant drop in temperatures worldwide. The aftermath would have disrupted food chains and habitats, causing a severe decline in species survival. Today, the asteroid impact theory is one of the most widely accepted explanations for the sudden disappearance of the dinosaurs.

Iridium Anomaly

The presence of iridium in rock layers from the time of the dinosaurs' extinction is known as the Iridium Anomaly. Iridium is a rare element on Earth's surface, but it is more common in asteroids and other extraterrestrial objects. In the early 1980s, scientists discovered unusually high concentrations of iridium in sedimentary layers dating back 65 million years. This discovery provided crucial evidence supporting the asteroid impact theory, as such iridium levels are consistent with an asteroid collision depositing this rare element worldwide. The Iridium Anomaly is a key piece of evidence that helps scientists understand the events leading to the mass extinction of the dinosaurs.

Scientific Theory

A scientific theory is a well-substantiated explanation for a set of observations or phenomena, based on a body of evidence. It is more robust than a hypothesis and is generally accepted within the scientific community unless disproven by new evidence. The proposal that an asteroid impact caused dinosaur extinction is classified as a scientific theory. It is grounded in evidence such as the Iridium Anomaly and geological findings that support the impact event. Like all scientific theories, this explanation is open to scrutiny and testing, allowing it to evolve as more information becomes available, which is essential to the advancement of science.