![]() Many of them are completely dark, so can't support photosynthesis. The air inside the caves has 80% to 100% humidity, and up to 3% CO 2, and some CO and H 2, but almost no CH 4 or H 2S. They are dynamical systems that collapse and rebuild, but persist over decades. There is almost no chance of photosynthetic based organics, or of animals in a food chain based on photosynthetic life, and no overlying soil to wash down into them. The caves at Erebus are high altitude, yet accessible for study. The caves on Erebus are of especial interest for astrobiology as most surface caves are influenced by human activities, or by organics from the surface brought in by animals (e.g. It is thought that ice caves may exist on Mars – ice preserved under the surface in cave systems protected from the surface conditions. This makes it of special interest for studying oligotrophs – organisms that can survive on minimal amounts of resources. The life is sparse, mainly bacteria and fungi. The ice caves associated with the fumaroles are dark, in polar alpine environments starved in organics and with oxygenated hydrothermal circulation in highly reducing host rock. Erebus is notable for its numerous ice fumaroles – ice towers that form around gases that escape from vents in the surface. These results demonstrated a complex upper-volcano conduit system with appreciable upper-volcano magma storage to the northwest of the lava lake at depths hundreds of meters below the surface. By studying the refracted and scattered seismic waves, the scientists produced an image of the uppermost (top few km) of the volcano to understand the geometry of its "plumbing" and how the magma rises to the lava lake. Researchers spent more than three months during the 2007–08 field season installing an unusually dense array of seismometers around Mount Erebus to listen to waves of energy generated by small, controlled blasts from explosives they buried along its flanks and perimeter and to record scattered seismic signals generated by lava lake eruptions and local ice quakes. The active lava lake in this summit cone undergoes continuous degassing. In the center of the summit caldera is a small steep-sided cone composed primarily of decomposed lava bombs and a large deposit of anorthoclase crystals known as Erebus crystals. It is filled with small volume tephritic phonolite and phonolite lava flows. The summit caldera was created by an explosive VEI-6 eruption that occurred 18,000 ± 7,000 years ago. A conspicuous break in slope at approximately 3,200 metres calls attention to a summit plateau representing a caldera. The upper slopes of Mount Erebus are dominated by steeply dipping (~30°) tephritic phonolite lava flows with large scale flow levees. Lava flows of more viscous phonotephrite and trachyte erupted after the basanite. Erebus is the world's only presently erupting phonolite volcano. Slightly younger basanite and phonotephrite lavas crop out on Fang Ridge-an eroded remnant of an early Erebus volcano-and at other isolated locations on the flanks of Erebus. The oldest eruptive products consist of relatively undifferentiated and non-viscous basanite lavas that form the low broad platform shield of Erebus. The composition of the current eruptive products of Erebus is anorthoclase- porphyritic tephritic phonolite and phonolite, which are the bulk of exposed lava flow on the volcano. The bottom half of the volcano is a shield and the top half is a stratocone. Mount Erebus is classified as a polygenetic stratovolcano. Scientific study of the volcano is also facilitated by their proximity to McMurdo Station (U.S.) and Scott Base ( New Zealand), both sited on Ross Island approximately thirty-five kilometres away. The volcano is scientifically remarkable in that its relatively low-level and unusually persistent eruptive activity enables long-term volcanological study of a Strombolian eruptive system very close (hundreds of metres) to the active vents, a characteristic shared with only a few volcanoes on Earth, such as Stromboli in Italy. Characteristic eruptive activity consists of Strombolian eruptions from the lava lake or from one of several subsidiary vents, all within the volcano's inner crater. The summit contains a persistent convecting phonolitic lava lake, one of five long-lasting lava lakes on Earth. Mount Erebus is currently the most active volcano in Antarctica and is the current eruptive zone of the Erebus hotspot.
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