In time or length?
In time - a major cave can take 10 or 100s of thousands of years to develop, and if it still carries water it is still developing.
In length - anything from a few feet to the something like 390 miles so far known and measured inthe Flint Ridge / Mammoth system.
No. Most caves are formed out of limestone making that false.
Wookies live in trees, not caves.
The Maquoketa caves in Iowa were formed through years of natural non-glacial erosion.
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Limestone caves are formed through a process called chemical weathering. Rainwater, which is slightly acidic, dissolves the limestone rock over time, creating small cracks. These cracks then widen as more water flows through, eventually forming caves. Additionally, some limestone caves are formed through the erosion of underground rivers.
Other way round! Water and/or air are in caves.:-) Most of the world's caves have formed / are forming in limestone.
Karst caves, and it is the majority of caves; formed by acidic ground-water dissolving the limestone.
Erosional caves are formed by the action of water or wind.
They - or it? - are normal karst caves, formed in limestone by its dissolution by water. I believe they still carry a stream: if so they are still forming.
Worldwiode, many tens, perhaps a few hundred, of millions of years - as long as there have been karst uplands. Many that formed in that time no longer exist because the landscapes in which they developed have long been eroded away.
The two features formed by underground weathering are caves and caverns. Caves are natural underground chambers typically formed in limestone, while caverns are larger caves that often have unique formations such as stalactites and stalagmites.
Fissure, Talus, Solutional, Granite, Slate, Erosional, man-made, rare emerged Sea caves, Sea caves, and Sandstone caves.Most are created over millions of years by water dissolving minerals in the rock, leaving a void or hollow behind.