A big rock stands in the sea. 

A tall red rock stands in the sea. 


The Old Man of Hoy is a tall sea stack. 


The Old Man of Hoy is a famous sea stack. 

This rock pillar was formed by a thing called hydraulic action. This happens when strong waves hit a cliff with great force. The waves break the rock apart over time. The stack sits on a base of harder basalt rock. Its sides are made of layers of soft sandstone and harder flagstones. This gives the sides a notched look. The stack is separated from the mainland by a 60-metre chasm. High-energy waves and fast winds help erode the coast quickly. 
Maps show us how the stack changed over time. A map from 1600 shows a headland at this spot. A map from 1750 also shows a headland but no stack. By 1819, the stack was separate from the land. In 1817, it actually had two legs. 
Many brave people have climbed the stack. The first climb happened in 1966 by Chris Bonington, Rusty Baillie, and Tom Patey. In 1967, a BBC broadcast of climbing reached 15 million viewers. 
People do more than just climb this rock. Some people even walk on a thin line called a slackline. 

The Old Man of Hoy is a massive sea stack located on the island of Hoy. This island is part of the Orkney archipelago off the north coast of Scotland. A sea stack is a tall pillar of rock that stands alone in the ocean. 

Nature created this landmark through a process called hydraulic action. This happens when high-energy waves hit a cliff with great force. Over time, the power of the water erodes the rock. The Old Man of Hoy sits on a plinth of basalt rock. This basalt acts as a base for the sandstone above it. The sandstone itself consists of layers of soft, sandy, and pebbly material. It also contains harder flagstones. These different layers create a notched and slab-like profile on the sides of the stack. 
The environment around the stack is very intense. Winds are faster than usual for nearly a third of the time. On average, gales occur for 29 days every year. The sea is also very deep near the coast. These factors lead to rapid erosion of the western side of Hoy. The stack is currently separated from the mainland by a chasm. This gap is 60 metres, or about 200 feet, wide. The chasm is filled with fallen debris from the rocks. 
We can use history to see how much the landscape has changed. The stack is relatively young and is probably less than 250 years old. It does not appear in the Orkneyinga saga from the year 1230. A map from 1600 by Blaeu shows a headland instead of a stack. The McKenzie map of 1750 also shows a headland. However, by 1819, the stack had become separated from the mainland. 
Many skilled mountaineers have traveled to Hoy to climb the stack. The first ascent was completed in 1966 by Chris Bonington, Rusty Baillie, and Tom Patey. In 1967, a live BBC broadcast of a climb reached 15 million viewers. 

Younger people have also made incredible climbs on this rock. In 2018, 8-year-old Edward Mills climbed the stack in 4 hours and 55 minutes. He did this to raise money for a cancer charity. In 2023, 10-year-old Sophia Wood became the youngest female climber. She completed her climb in just over 3 hours. 
Beyond climbing, people use the stack for other extreme sports. In 2017, Alexander Schulz performed a highline walk. This involves walking on a long, thin line stretched from the summit. 
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