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University of Bergen
Geophysical Institute

24 days of kitchen oceanography

Each day a new experiement will be posted here. Reveal what is hidden behind the windows by clicking on the arrows below.

Introduction
Day 1
Day 2
Day 3
Day 4
Day 5
Day 6
Day 7
Day 8
Day 9
Day 10
Day 11
Day 12
Day 13
Day 14
Day 15
Day 16
Day 17
Day 18
Day 19
Day 20
Day 21
Day 22
Day 23
Day 24

Main content

Transport of substances

Day 12
12.12.2020

Why do the tea leaves end up in the middle of the cup?

Transport av stoffer
Photo:
Mirjam Glessmer, GFI

Experiment 12: 

By stirring in a tea cup (or, as shown in the picture, a cup of water with ground pepper in it), we force water to the edge. There, it sinks to bring the water level back to horizontal. As water continues to be pushed to the edge by the constant stirring, water has to rise in the middle of the cup to replace the water that was pushed to the outside and sank. Tea leaves are carried by current on the ground towards the center of the cup. But they are too heavy to be lifted up with the water, so they accumulate in the middle.

Chapter 12: Transport of substances

Some substances are transported by ocean currents but have a different density than the water. Therefore, they either float on top (like plastic garbage) or stay near the bottom (like sediment). They accumulate in areas when water rises or sinks, when they can’t keep up because of their different density.