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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.

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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
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Day 20
Day 21
Day 22
Day 23
Day 24

Main content

Overflows

Day 5
05.12.2020

Why is there a blue waterfall tumbling over the white threshold?

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Photo:
Mirjam Glessmer, GFI

Experiment 5: 

We build a playdough dam in a rectangular plastic container, separating two similarly sized basins at about half the container depth, representing an oceanic ridge. We then fill the container with lukewarm water and place a frozen cool pack over one edge. Blue food color, dripped continuously on the cool pack, marks the water that is cooled there and sinks to the bottom. Gradually, as more and more water cools and sinks, and the reservoir on the cooling pack’s side of the dam fills up with cold, blue water. When the cold, blue water pool has filled up to the lowest point of the ridge, the water begins to flow over the ridge. A waterfall forms when the cold, dense blue water sinks below the less dense water on the other side of the ridge.

Chapter 5: Overflows

In addition, currents are influenced by the shape of coasts and the seabed. Sometimes, for example, ocean basins are separated by oceanic mountain ranges, called ridges. If a reservoir with dense water is formed on one side of such a ridge, it might eventually fill up the whole basin to the level of the lowest part of the ridge. If then any denser water is added, it spills over the ridge and creates an overflow of dense water.