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Sea-based blowhole Land-based blowhole. In geology, a blowhole or marine geyser is formed as sea caves grow landward and upward into vertical shafts and expose themselves toward the surface, which can result in hydraulic compression of seawater that is released through a port from the top of the blowhole. [1]
The Pancake Rocks are a heavily eroded limestone formation where the sea bursts through several vertical blowholes during incoming swells, particularly at high tide. The limestone was formed in the Oligocene period (around 22–30 million years old), a period in the geological history of New Zealand where most of the continent of Zealandia was submerged beneath shallow seas. [2]
The Smackover Formation is a geologic formation that extends under parts of Arkansas, Louisiana, Texas, Alabama, Mississippi, and Florida. [1] It preserves fossils dating back to the Jurassic period. The formation is a relic of an ancient sea that left an extensive, porous, and permeable limestone geologic unit.
[1] Primitive rocks "have never been heated much, although some of their constituents may have been quite hot early in the history of our Solar System. Primitive rocks are common on the surfaces of many asteroids, and the majority of meteorites are primitive rocks." [1]: 145 Widmanstätten pattern in an iron-rich meteorite
The group ranges in age from Paleocene to Eocene and is in Texas subdivided into the Calvert Bluff, Simsboro and Hooper Formations, [1] and in Alabama into the Nanafalia and Hatchetigbee Formations. [2] [3] Other subdivisions are the Lower, Middle and Upper Wilcox Subgroups, and the Carrizo and Indio Formations. [4]
The formation was named by E. O. Ulrich in 1911 for the town of Chepultepec (now Allgood). [6] The Chepultepec Formation is a primarily limestone and dolomite formation, the earliest formation of the Ordovician period in its area. Further north, it is equivalent to the Stonehenge Formation of the Beekmantown Group. [12]
QAPF diagram for the classification of plutonic rocks Devils Tower, United States, an igneous intrusion exposed when the surrounding softer rock eroded away. Intrusive rock is formed when magma penetrates existing rock, crystallizes, and solidifies underground to form intrusions, such as batholiths, dikes, sills, laccoliths, and volcanic necks.
On windy days when the tide is high, the ocean breeze sends the waves rolling on to the shore where the rock formation then shoots sea spray high into the air through the cave acting like a geyser. The blowhole is most active when the tide is high and the winds are strong, [3] and it can shoot sea spray up to thirty feet high in the air. [4]