Where Is the Biggest Waterfall in the World?
The short answer
Underwater, between Greenland and Iceland. The Denmark Strait cataract is the largest waterfall on Earth by flow and by height. It carries more than 1,000 times the water of Niagara Falls and slides more than 2 km down a slope under the sea. You can't see it, because it's water falling through water.
Cataract is an old word for a big waterfall. The eye condition shares the name.
How water falls through water
Cold water is denser than warm water. The water coming from the Arctic side of the strait is colder than the Atlantic water around it. So it sinks and slides underneath. It pours over an undersea ridge about 610 m (2,000 ft) below the surface and runs down the slope to about 3,048 m (10,000 ft). That's a drop of roughly 2,400 m (8,000 ft).
The sea surface above it stays flat. Without scientific instruments, nobody would know the cataract is there. Scientists measure it with current meters moored on the sea floor and with surveys from ships.
Slow, but enormous
At the ridge, the cataract carries about 3.2 to 3.5 million cubic meters of water a second. In daylight during the tourist season, at least 2,832 cubic meters (100,000 cubic feet) a second must go over Niagara Falls. Divide one by the other and the cataract works out to about 1,130 to 1,250 Niagaras.
It isn't fast, though. Changes in its water take about 13 days to travel 500 km downstream from the ridge. That's roughly 0.45 m a second, slower than walking pace. A drop going over Niagara's Horseshoe Falls falls 57 m (188 ft) in about 3.4 seconds.
That's the trick behind the race in the film. Each second, the cataract moves more than 1,000 times as much water as Niagara. So whatever lake the two race to empty, the cataract needs less than a thousandth of Niagara's time. Niagara's more than 5 years for Lake Erie becomes the cataract's under 2 days.
The dimmer and the missing off switch
The 1950 Niagara Treaty sets how much water must go over the falls. In daylight during the tourist season, it's at least 2,832 cubic meters (100,000 cubic feet) a second. At night, and outside the tourist season, it's half that: 1,416 cubic meters (50,000 cubic feet) a second. Water above those minimums can go through tunnels to power stations on both sides of the border.
The cataract has no switch. Moored instruments at the ridge have measured it since 1996. From 1996 to 2016 it averaged about 3.2 million cubic meters a second, with no significant trend.
Key numbers
| What | Number | Source |
|---|---|---|
| Depth of the cataract, from the top of the ridge to the bottom of the slope | about 610 m (2,000 ft) down to about 3,048 m (10,000 ft) | NOAA Ocean Service, Where is Earth's largest waterfall? |
| Height of the drop | about 2,400 m (8,000 ft), more than 2 km | Our arithmetic from NOAA Ocean Service, Where is Earth's largest waterfall? |
| Average flow at the ridge, 1996 to 2016, from moored instruments | about 3.2 million m³ a second, no significant trend | Jochumsen et al. 2017, JGR Oceans |
| Average flow at the ridge from ship surveys, 1993 to 2018 | about 3.54 million m³ a second | Lin et al. 2020, Journal of Physical Oceanography |
| Minimum flow over Niagara Falls, daylight in the tourist season | 2,832 m³ (100,000 cubic feet) a second | Niagara Parks, Niagara Falls geology facts and figures |
| Minimum flow over Niagara Falls, at night and outside the tourist season | 1,416 m³ (50,000 cubic feet) a second | Niagara Parks, Niagara Falls geology facts and figures |
| The cataract's flow measured in Niagaras | about 1,130 to 1,250 | Our arithmetic from Jochumsen et al. 2017, JGR Oceans; Lin et al. 2020, Journal of Physical Oceanography; Niagara Parks, Niagara Falls geology facts and figures |
| Drop of the Horseshoe Falls, and the time to fall it | 57 m (188 ft), about 3.4 seconds | Our arithmetic from Niagara Parks, Niagara Falls geology facts and figures |
| Time for changes in the cataract's water to travel 500 km downstream | about 13 days | Jochumsen et al. 2015, JGR Oceans |
| Speed at which those changes travel downstream | about 0.45 m a second | Our arithmetic from Jochumsen et al. 2015, JGR Oceans |
What the film simplifies
- Niagara says a drop takes 3 seconds from top to bottom. A free fall down the Horseshoe Falls' average drop of 57 m (188 ft) takes about 3.4 seconds.
- "Weeks" is how long changes in the cataract's water take to travel about 500 km downstream from the ridge, about 13 days. The cataract is a long slope, not a cliff, so it isn't the same kind of trip as a drop going over Niagara.
- The Niagara comparisons use the treaty's minimum for daylight in the tourist season, 2,832 m³ a second. At night the treaty minimum is half that.
- The film says Niagara gets turned down at night. The lower minimum of 1,416 m³ (50,000 cubic feet) a second also applies all day outside the tourist season.
- "Use a thermometer" is shorthand. Scientists use instruments that measure temperature and currents, lowered from ships or moored on the sea floor, and the temperature map in the film is drawn, not real data.
- The talking waterfalls, the crown, the bathtubs shaped like Lake Erie and the wall dimmer are cartoon.
At a glance
Runtime 1 minute 6 seconds · Topics: Ocean currents, Density, Waterfalls · Captions on YouTube · Full script below
Test yourself
How can water fall through water?
Answer
Cold water is denser than warm water. The colder water from the Arctic side sinks under the warmer Atlantic water and slides down the slope beneath it.
The cataract carries about 3.2 million cubic meters of water a second. Niagara's minimum in daylight during the tourist season is 2,832 cubic meters a second. About how many Niagaras is the cataract?
Answer
About 1,130, which is why the film says more than 1,000.
The cataract's water moves slower than you walk. How can it still empty Lake Erie in under 2 days when Niagara needs more than 5 years?
Answer
Speed isn't the same as flow. The cataract is so big that even at about 0.45 m a second it moves more than 1,000 times as much water each second as Niagara.
The script
The Underwater Falls: Mine. I'm the biggest waterfall on Earth!
Niagara Falls: Pal, I'm Niagara Falls. Nobody can see you!
The Underwater Falls: I'm right here! Denmark Strait, between Greenland and Iceland.
Niagara Falls: I see flat water. And a seagull.
The Underwater Falls: It's sitting right over me!
The Underwater Falls: Colder than your fridge. So I sink!
Host: He slides under the warmer water.
The Underwater Falls: More than 2 kilometers down.
Host: Water falling through water. You can't even see it.
The Underwater Falls: Then use a thermometer, genius!
Niagara Falls: 3 seconds, top to bottom!
The Underwater Falls: ...Weeks.
Niagara Falls: Folks, you walk faster than that!
The Underwater Falls: Race you! Who empties Lake Erie first?
Niagara Falls: My own lake?
Host: Niagara Falls would need more than 5 years.
The Underwater Falls: Done in under 2 days!
Host: Slow, but enormous. That's more than 1,000 Niagaras.
Niagara Falls: Still, I'm the show. Day and night!
Host: At night, by treaty, Niagara's water gets turned down. By half.
The Underwater Falls: Ha! A dimmer? Nobody turns me down!
Niagara Falls: Ponchos. Half price, folks.
Sources
- The largest waterfall on Earth is in the ocean beneath the Denmark Strait, between Greenland and Iceland. It begins about 2,000 ft below the surface and plunges to about 10,000 ft. Cold water sinks because it is denser than warm water. It goes undetected without scientific instruments.NOAA Ocean Service, Where is Earth's largest waterfall?
- The Denmark Strait cataract is the world's largest waterfall, hidden underwater.Live Science, Denmark Strait cataract
- The overflow at the Denmark Strait averaged about 3.2 million m³ a second from 1996 to 2016, measured by moored instruments, with no significant trend.Jochumsen et al. 2017, JGR Oceans
- Changes in the overflow water take an average of 13 days to travel from the Denmark Strait sill to an array about 500 km downstream (180 km plus a further 320 km).Jochumsen et al. 2015, JGR Oceans
- Ship surveys from 1993 to 2018 give a mean overflow of about 3.54 million m³ a second at the Denmark Strait sill.Lin et al. 2020, Journal of Physical Oceanography
- How the Denmark Strait overflow plume mixes with surrounding water as it runs downstream (background, listed in the film's sources).Voet and Quadfasel 2010, Ocean Science
- Under the 1950 treaty, at least 100,000 cubic feet (2,832 m³) a second must go over Niagara Falls in daylight in the tourist season, and 50,000 cubic feet (1,416 m³) at all other times, including night. The Horseshoe Falls drops an average of 57 m (188 ft).Niagara Parks, Niagara Falls geology facts and figures
- Water diverted from the Niagara River goes through tunnels to power stations on the US and Canadian sides.International Control Dam, Wikipedia