Lava cave: Difference between revisions

 

=== Inflationary caves ===

Inflationary caves tend to be small chambers that form when lava is pressurized and pushes exterior rock. The lava may then later drain leaving an inflationary cave. In some cases, volcanic gases may exert pressure on solid or semi-solid lava and form what is basically a bubble of thin rock called a blister. These blisters are at times big enough to qualify as a cave. Inflated caves can be mistaken for lava tubes because they often share many of the same characteristics.<ref name="CHITWOOD"/> An example of inflationary caves can be found in [[pressure ridge (lava)|pressure ridges]]. Pressure ridges are fractured lobes of hardened lava and may occasionally be hollow.

 

 

=== Open vertical conduits ===

Open vertical conduits, or OVCs, are vertical passages through which lava rose to the surface then receded.<ref name="LARSON2"/> They have a round or oval-shaped passage.<ref name="SKINNER">

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=== Pit craters ===

{{Main|Pit crater}}

Pit craters form when magma that doesn’t quite reach the surface drains to form a void, and the ground above it slumps. These huge open-air pits, with their sheer walls, are analogous to some of the large shafts that formed by solution, and typically require a roped descent for exploration. While most have no extension beyond the visible floor, others may have entrances into adjacent (now empty) magma chambers, such as was seen when the crater of Mauna Ulu in [[Hawai`i Volcanoes National Park]] was explored by a team of Swiss cavers. In Na One, a pit crater on [[Hualālai]] Volcano in [[Hawaii]], a narrow opening at the bottom of an {{convert|430|ft}}-deep pit crater leads into an open vertical volcanic conduit, with a total depth of {{convert|880|ft}}.<ref>{{cite journal |last=Halliday |first=W.R. |date=November 1995 |title=A record year in Hawaii |journal=NSS News}}</ref>

 

=== Rift caves ===

Rift or fissure caves, form along volcanic rift zones and eruptive fissures, or in fractures associated with volcanic activity. These are tectonic in formation, caused by ''stress in lava during and after solidification.'' They may also be the site of fissure eruptions, and the walls covered with spatter. Notable rift caves include Crystal Ice Cave, formed in Idaho’s Great Rift (and now part of [[Craters of the Moon National Monument and Preserve]]). Caves in the Great Rift are known up to {{convert|800|ft}} deep.

 

=== Lava mold caves ===

[[Image:Pietracannone.JPG|thumb|A lava mold of a tree trunk]]

Lava mold caves, sometimes erroneously called "lava casts", form when lava flows around trees ([[lava tree mold]]s) or even large dead animals. The engulfed material eventually burns or decays away, but ends up leaving a hollow space with the original shape. Usually these are not very large but can get somewhat complex where groups of fallen logs were touching, and may then form caves that go in several directions where the resulting voids intersect. Such caves are known from [[Washington (U.S. state)|Washington]] (US), near [[Ape Cave]], and most notably from Japan in the Yoshida-tanai area. [[Elephant]] mold caves are known from the [[Nyiragongo]] volcano in Africa, and one in the shape of a [[Tertiary]]-age [[rhinoceros]] is known from [[Blue Lake (Washington)|Blue Lake]], Washington.<ref name="Chappell et al., 1951">Chappell, W.M.; Durham, J.W. & Savage, D.E. (1951): Mold of a Rhinoceros in Basalt, Lower Grand Coulee, Washington. ''Bulletin of the Geological Society of America'', 62(8): 907–918.</ref><ref name="Kaler, 1988">Kaler, K.L. (1988): The Blue Lake Rhinoceros. ''Washington Geologic Newsletter'', 16(4): 3–8.</ref>

 

== References ==