What Is a Pressure Ridge?

A pressure ridge is the term for a protruding formation made of either ice or lava. When such a ridge forms in ice, it is usually the result of fluctuating temperatures on the surface of a lake or, in the case of an ocean, sea ice. Pressure ridges composed of lava generally form after a top layer of hardened lava is pushed up by molten lava below. These occurrences may be of interest to glaciologists, who study the natural processes of ice, or volcanologists, who study volcanoes and lava as well as the resulting formations.

When the surface of a body of water freezes in cold temperatures, whether on lake or the surface of the ocean, a pressure ridge can form. If the surface of the frozen water repeatedly melts and cools, this will cause contraction and expansion, and a crack can occur as a result. In extremely cold temperatures, it is possible that the ice will contract further, causing gaps between these cracks. These cracks will sometimes fill with water, which also freezes. If the temperature rises at a later time, this ice will expand and force itself out of the crack, causing a protruding ridge which can extend upwards for 10 feet (about 3 meters) or more.

Pressure ridges made of ice should not be confused with the occurrence of rubble ice. Rubble ice is a grouping of fragmented ice that covers a much larger expanse of a frozen surface. It is also much lower in height than a pressure ridge.

When lava is flowing, it is possible for it to form a pressure ridge, which may also be referred to as a tumulus. This can occur when the outermost surface of the lava begins to become hard and the still molten lava below begins to push against it from beneath. As a result, elevated mounds of hardened lava can appear, varying in height and length.

Small enclosures can occur as a result of a lava pressure ridge, and are usually identified as inflationary caves. This is not common but can occur when the lava hardens with a hollow inner section. The inside of these small caves usually become hollow when the outer surface hardens and the molten lava that caused the pressure ridge to occur finds a way to escape.

A pressure ridge is a geological formation typically found on ice sheets or glaciers, where the ice has been pushed upwards by the force of colliding ice floes. This phenomenon occurs due to the thermal expansion, contraction, and the movement of the ice, causing it to buckle and form ridges that can be several meters high.

Pressure ridges form when two ice masses, such as those in frozen lakes, sea ice, or glacial fronts, push against each other. The immense pressure causes the ice to crack and pile up into ridges. These structures can grow both above and below the ice surface, creating complex networks of ridges and keels.

Pressure ridges are commonly found in polar regions, particularly in the Arctic and Antarctic, where sea ice is prevalent. They can also occur on large freshwater bodies that freeze over, such as the Great Lakes in North America, during the winter months when temperature fluctuations and wind contribute to ice movement.

Studying pressure ridges is crucial for understanding ice dynamics and the health of polar ecosystems. They influence local wildlife habitats and are indicators of climate change. According to research, changes in the frequency and size of pressure ridges can reflect alterations in environmental conditions, making them valuable for climate scientists.

Yes, pressure ridges can pose significant risks to human activities such as shipping, offshore drilling, and ice fishing. They can create hazardous conditions for vessels navigating ice-covered waters and for infrastructure on or near the ice. Understanding their formation and distribution is essential for safe operations in polar regions.

Pressure ridges have a profound impact on the local ecosystem. They create diverse habitats for marine life, with the ridges and associated leads providing breathing holes for mammals like seals and polar bears. The ridges also influence the distribution of nutrients and light penetration, affecting the under-ice ecosystem and the broader food web.