How geologists tell time?

Answer 1

Rocks

Rocks have many mysteries to them. Many geologists study the rocks to find out the history of earth. What happened in the past? How was it back then? Have you ever wanted to know what the history of your ancestors? Well the same for geologists, they study it to see what was the weather conditions in the past, how old was the rock, was it eroded, and many other things. To determine that, geologists use their tools to find out all these things. One main tool they use is relative dating, or the sequence in which an event took place. For example, if a geologist fined a rock that was cracked almost half way, he/she will predict that an earthquake took place then wind came and eroded it. Basically, relative dating is saying first, second, third etc.

However, when geologists bring the exact time something happens it is called absolute dating. Another thing about rocks is, most of the rocks are layered. The bottom layer of the rock is the oldest and the top is the youngest. When a piece of the rock is missing it is called unconformity. Some of the layers in the rock is larger or smaller than the other layer. This is due to compression for sun light or heat. Some layers may be exposed to the sun and some not. Another tool that is used is relative age. Relative age is when geologists bring two rocks from different places but they are the same age. They examine it to see the differences in these two rocks to see the effects on each environment.

This is a figure of layers of a rock. This layer is made of many different types of rocks. As shown in the picture some of the layers are large and some are small. Some are dark and some are light. The top is the youngest and the bottom is the oldest. The layers show you the ages of the rocks.

Erosion is when weather conditions happen and it moves materials from one place to another using snow, hail, rain, waves, wind etc. Geologists try to discover what happened in the past that made the rocks go from one place to another. Did an earthquake occur? A volcano eruption? A storm? This is one way how rocks travel around the world. This is how sometimes unconformity happens.