Wikipedia
A pressure ridge develops in an ice cover as a result of a stress regime established within the plane of the ice. Within sea ice expanses, pressure ridges originate from the interaction between floes, as they collide with each other. Currents and winds are the main driving forces, but the latter are particularly effective when they have a predominant direction. Pressure ridges are made up of angular ice blocks of various sizes that pile up on the floes. The part of the ridge that is above the water surface is known as the sail; that below it as the keel. Pressure ridges are the thickest sea ice features and account for about one-half of the total sea ice volume. Stamukhi are pressure ridges that are grounded and that result from the interaction between fast ice and the drifting pack ice.
A pressure ridge sometimes referred to as a tumulus (or tumuli in plural form) is created in an active lava flow. Formation occurs when the outer edges and surfaces of the lava flow begin to harden. If the advancing lava underneath becomes restricted it may push up on the hardened crust, tilting it outward. Inflation also takes place and is a process where the plastic layer of lava underneath expands as it cools and small crystals form. The end result is a raised mound of hardened lava rock, usually a relatively narrow but long ridge. Tension cracks form on the surface of pressure ridges and run along the axis of elongated ridges, and at both edges of broader ridges, sometimes referred to as pressure plateaus. Sometimes, along the edges of a pressure ridge, the tension crack can be large enough to create a liftup cave. Other caves can form inside pressure ridges when the lava vacates leaving an inflationary cave.
Pressure ridge may refer to:
- Pressure ridge (ice): Results from the interaction between expanses of sea ice.
- Pressure ridge (lava): Surfaces pushed up in lava flows
Usage examples of "pressure ridge".
A combination of a current where a current had no right to be, a temperature inversion where a temperature inversion had no right to be, and a pressure ridge where we least expected it.
To get to the food, which was on top of a pressure ridge, he had to collect the climbing equipment to reach it, but the climbing gear was too bulky and heavy to carry in the backpack.
White, fluffy stratus clouds slid along a pressure ridge to the north, appearing to keep pace with him as he jogged along the ridgetops, across the long hills leading toward home.
No storms were expected despite the low-pressure ridge, and Passover—.
No storms were expected despite the low-pressure ridge, and Passover -- the ominous conjunction of the three moons that produced the fiercest storms -- was nine weeks away.
And there was a hollowed-out area of snow near a pressure ridge, marked by black excrement, where the bear had probably slept after its bloody feast.
Behind this was a deeper, more violent sound which Gerda told me was a pressure ridge building up amongst a solid area of pack.