Mahoney - Geologic Time Task Quiz

Explanation
The answer "Humans have been on Earth for a very short time" is correct because in geological terms, the existence of humans is relatively recent. The Earth is estimated to be around 4.5 billion years old, while human beings have only been present for approximately 200,000 years. This makes the duration of human presence on Earth relatively short compared to the overall age of the planet.

Explanation
The Precambrian time period was the longest among the four listed. It spans from the formation of the Earth, around 4.6 billion years ago, to the beginning of the Cambrian period, approximately 541 million years ago. This period is characterized by the absence of complex life forms and is divided into three eons: Hadean, Archean, and Proterozoic. It represents a significant portion of Earth's history, encompassing billions of years before the emergence of multicellular organisms and the subsequent diversification of life during the Paleozoic, Mesozoic, and Cenozoic eras.

Explanation
The Cenozoic era is the current time period that began around 66 million years ago and is characterized by the dominance of mammals and the diversification of life forms. It is also known as the Age of Mammals. This era followed the Mesozoic era, which was known for the dominance of dinosaurs and ended with a mass extinction event. The Cenozoic era is marked by significant geological and biological changes, including the evolution of humans. Therefore, it is correct to say that we are currently living in the Cenozoic era.

Explanation
The age of the earth is estimated to be around 4.6 billion years old. This estimation is based on various scientific methods, including radiometric dating of rocks and minerals. By analyzing the radioactive decay of certain elements, scientists have been able to determine the age of the oldest rocks on Earth, which provides evidence for the earth's age. Additionally, studies of meteorites and moon rocks have also provided further support for this estimate.

Explanation
During the Mesozoic era, dinosaurs roamed the land. This era, also known as the Age of Reptiles, lasted from approximately 252 to 66 million years ago. It is characterized by the dominance and diversification of dinosaurs, as well as the emergence of other reptiles such as pterosaurs and marine reptiles. The Mesozoic era is divided into three periods: the Triassic, Jurassic, and Cretaceous. It was during these periods that dinosaurs flourished and evolved into a wide variety of species, occupying various ecological niches on land.