The Loch Ness monster lives in a giant carpenter's level.
Just as the bubble in a carpenter's level moves back and forth depending on the surface it rests upon, Scotland's Loch Ness tilts back and forth according to the movement of the ground beneath it caused by the tides on the nearby North Sea. The motion is so subtle GPS couldn't even track it.
When the tide comes in on the North Sea, 13 kilometers (8 miles) to the east of Loch Ness, the increased pressure on the seafloor deforms the Earth, a process called ocean tidal loading. And while the moon controls the tides of the North Sea, and affects the loch as well, the wobbly movement of the land from the pressure of the changing tides is what really determines the loch's levels. The water in the loch acts like a bowl of water on a wobbly table, sloshing according to the movement of the land it rests upon.
The depth of the loch changed by 1.5 millimeters (0.06 inches) at its different ends depending on whether the North Sea tide was in or not, according to researchers at the National Oceanography Center in the UK and the University of Porto, Portugal.
The researchers used pressure sensors distributed throughout Loch Ness to measure depth changes to the incredible accuracy of 0.1 mm (0.004 in) over the 35 km (22 mi) length.
"Our tilt accuracy of better than 10−8, measured over 35 km, demonstrates Loch Ness as one the world's longest and most accurate tiltmeters," the researchers said in the abstract of their paper published in the Journal of Geophysical Research.
These measurements may be a first for a European lake with land shifting tides due to ocean tidal loading.
Loch Ness with Urquhart Castle in the foreground. (Sam Fentress, Wikimedia Commons)