Activity

Ocean sediment cores

Summary
Look at images of ocean sediment cores to see evidence of the greenhouse warming period 55 million years ago, and that the oceans gradually recovered.
Science content
Earth/Space: Sustainable practices, Interconnectedness (2, 5, 7)
Earth/Space: Fossil records, Geologic time scale (7)
Science competencies (+ questioning + manipulation + others that are in every activity)
Processing/analyzing: classifying data, finding patterns (1 up)
Evaluating: inferring (3 up)
Procedure

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. Few 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, and there was mass release of methane from sediments on the sea floor (which was oxidized to CO2 in 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, leading to extinction of deep sea shelled animals.
(The PETM was not the cause of extinction of the dinosaurs: PETM occurred approximately 10 million years after the Cretaceous mass extinction.)
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.

https://en.wikipedia.org/wiki/Paleocene%E2%80%93Eocene_Thermal_Maximum
https://www.palaeontologyonline.com/?p=1132

Grades taught
Gr 6
Gr 7