The ocean covers more than 70 percent of the Earth and holds many clues about past climate conditions. These clues can be found buried in the ocean floor in the form of tiny fossil shells. These shells were created by tiny, free-floating animals called plankton. Plankton, like many other organisms, adapt to live in specific climate conditions, like warm or cool ocean waters. When conditions change too much, plankton move to new locations or die. As plankton die, their shells sink to the ocean floor where they are slowly buried under layers of sand, mud, and more shells. Those layers are called sediment. Over time, more layers are added, creating a deep record of ancient organisms and the climate in which they lived.
How do scientists get samples of the deep ocean floor? They dig for it! Scientists use a technique called coring to drill or into the ocean floor, capturing layers of sediment in a long, narrow tube. The coring tube is slowly pulled out and can be more than 100 feet long, representing thousands or even millions of years of climate history. Once out of the ocean, scientists examine the core for climate clues. The oldest clues are always from the deepest part of the core. Try coring for yourself!
See activity below
Creating an ocean floor (image or picture of a layered cup & a second image of the cup with a straw in it)
Play-Doh, 4 different colors
Clear plastic or glass cup
Clear plastic straw(s)
Red and blue glitter
Flour or sand
Mix the red and blue glitter into two different colors of Play-Doh, one color of glitter per color of Play-Doh. Next, combine blue and red glitter into a third color of Play-Doh. Leave one color of Play-Doh plain.
In a clear cup, sprinkle a thin layer of flour or sand to keep the Play-Doh from sticking to the cup. Put a layer of blue glitter Play-Doh, 1 inch thick on the bottom. Make a second layer using the red/blue glitter Play-Doh, 1/2 inch thick. Make a third layer using the red glitter Play-Doh 1 1/2 inches thick. Finally, make a top layer of plain Play-Doh, 1/4 inch thick.
Coring for Clues
Now that you have made an ocean floor from which to take a core sample, start drilling. Place the straw into the ocean floor cup. Make sure you have gone all the way to the bottom of the cup. Slowly twist the straw, back and forth, to loosen the Play-Doh core from the layers. Place your thumb on the top of the straw and slowly pull the straw out of the Play-Doh.
Observe the layers of your ocean floor and the fossil “clues” that are buried within. The glitter represents the shells of ancient plankton once living in the ocean. The colors represent different types of plankton, ones that preferred warmer waters (red) and ones that preferred cooler waters (blue). From these “clues” can you make a prediction about what the plankton’s past climate was like and how it might have changed over time?
(Answer Upside down: The climate changed from cool to warm. Cool-water plankton shells were in the deeper (older) sediment layers and disappeared in upper layers. Warm-water plankton shells appeared in upper (younger) layers of sediment, but not in the oldest layers.)