Question

The Cenozoic Era has lasted 65 million years. What percentage of Earth's 4.5-billion-year history is that?

Short answer

Approximately 1.44% of Earth's history is the Cenozoic Era.

Step-by-step solution

Understand the Problem

We need to find what percentage 65 million years is of 4.5 billion years. This is a problem of proportions, where we want to express one time period as a percentage of another.

Convert Units to a Common Scale

First, ensure both time periods are in the same units. The Cenozoic Era's 65 million years is already in millions, and Earth's history of 4.5 billion years is equivalent to 4500 million years (since 1 billion equals 1000 million).

Set Up the Percentage Calculation

To find out what percentage 65 million is of 4500 million, use the formula:\[\text{Percentage} = \left( \frac{\text{Part}}{\text{Whole}} \right) \times 100\]Here, the Part is 65 million and the Whole is 4500 million.

Calculate the Percentage

Plug the values into the formula: \[\left( \frac{65}{4500} \right) \times 100\]Calculate the fraction first, which is approximately 0.0144. Then multiply by 100 to convert to a percentage, yielding approximately 1.44%.

Key concepts

Cenozoic Era

The Cenozoic Era is a fascinating and important period in Earth's history. It began about 65 million years ago, right after the mass extinction event that marked the end of the dinosaurs and the Mesozoic Era. This era is often referred to as the "Age of Mammals" because during this time mammals became the dominant land animals. It continues up to the present day. During the Cenozoic Era, the Earth experienced many significant changes, including shifts in climate that led to the development of current flora and fauna. The era is divided into two periods: the Tertiary and Quaternary. Each of these periods highlights important evolutionary events and ecological shifts. Understanding this era provides valuable insight into how past climate and environmental changes have shaped the living world as we see it today.

Percentage Calculation

Calculating percentages is a practical skill that is widely used in various fields, including Earth science when dealing with large time scales. A percentage represents a part out of a whole as parts per hundred.
To calculate a percentage, you use the formula:

• Percentage = \( \left( \frac{\text{Part}}{\text{Whole}} \right) \times 100 \)

This formula is useful for comparing different quantities, such as determining how much of Earth's history the Cenozoic Era covers. By expressing the fraction of the eras in percentage terms, it becomes easier to grasp the scale of each time period in relation to Earth's entire history. This process involves simple division and multiplication and breaks down an often overwhelming amount of data into understandable segments.

Proportions in Earth Science

Proportions play a crucial role in Earth science, especially when dealing with vast stretches of time like the history of our planet. Proportionality helps scientists make sense of the relationships between different geological eras and events. For example, understanding what fraction of Earth's history is occupied by the Cenozoic Era, compared to the total history since the planet formed, allows us to conceptualize its significance.
When students learn about proportions in Earth science, it helps them to quantify and compare different time periods, aiding in the visualization of geological timelines. By expressing these eras as proportions, one can easily compare the relative lengths and impacts of different geological events on Earth's evolution.

Time Periods in Geology

Geological time periods are large spans of time that help us understand Earth's complex and dynamic history. They are divided into eons, eras, periods, epochs, and ages, each representing significant phases in Earth's past marked by distinct climate conditions, biological evolution, and continental arrangements. The use of these time divisions enables geologists to study Earth's history in manageable segments.
Each time period is identified based on its unique characteristics and fossil records. For instance, the Mesozoic Era is noted for the age of reptiles, while the Cenozoic Era is famously known as the age of mammals. Learning about these time scales helps students appreciate the long and intricate history of the planet, and provides context for current geological and environmental phenomena. Understanding these time periods is fundamental to understanding the Earth's history and aids in recognizing patterns that have repeated over millions of years.