Tree Rings, Ice Cores, and Varves

Did you know that trees, ice, and even lake sediments can help us learn about Earth's past?

Let's start with tree rings. If you cut into a tree, you'll see rings. Each light band shows summer growth, and each dark band shows winter growth, representing one year together. Scientists can count these rings to determine the tree's age.

If the ring is wide, it indicates a good year with plenty of water. But if it is narrow, it shows a dry season.

Now, imagine a glacier. Each year, snow falls in winter, and dust settles in summer, creating layers in the ice.

Scientists drill out cylinders of ice called ice cores to study these layers. They study trapped gas bubbles in the ice core to understand changes in the atmosphere and climate.

Finally, let's look at lake sediments. In glacier-fed lakes, melting ice deposits thick layers of sediment in summer and thin, clay-rich layers in winter. These layers, called varves, help scientists understand past climates.