Ocean sediment cores

Tell students that sediment layers at the bottom of the ocean show changes in Earth’s atmosphere millions of years ago.
Optionally show an image of how core samples are collected e.g. https://images.ctfassets.net/kzewhs8e6cvu/7GhngoRnVhczSssydtnh5Q/78daa1…

Distribute images of ocean sediment core. Demonstrate how core samples are collected. Younger at the top, older at the bottom.
What do you notice in the colours of the core samples?
The whiter parts are shells of ocean animals. When the animals died their shells fell to the ocean floor, layering and compressing into white rock (called limestone).
The red is clay. No shells fell to the bottom of the ocean where it is red.
The white-red boundary is from a huge burst of greenhouse gases in the atmosphere, 55 million years ago, when volcanoes released a huge amount of CO2 into the atmosphere. Called the Paleocene–Eocene Thermal Maximum.
This massive carbon release into the atmosphere lasted from 20,000 to 50,000 years. The entire warm period lasted for about 200,000 years. Global temperatures increased by 5–8 °C.
The change of CO2 in the atmosphere changed the ocean.
At our current rate of emissions, we are releasing CO2 into the air faster than the PETM.

BUT, see how the ocean sediments gradually recovered, turning white again as the atmospheric CO2 decreased, so decreasing CO2 in the ocean.
If we choose as a society to vastly reduce emissions, the oceans will recover.. The movement is growing to make it happen.