Mount Porndon is a
Stratovolcano
A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and per ...
located 13 kilometres southeast of
Camperdown in western
Victoria,
Australia
Australia, officially the Commonwealth of Australia, is a Sovereign state, sovereign country comprising the mainland of the Australia (continent), Australian continent, the island of Tasmania, and numerous List of islands of Australia, sma ...
.
Mount Porndon is on private land. There is a
fire tower on the
summit
A summit is a point on a surface that is higher in elevation than all points immediately adjacent to it. The topography, topographic terms acme, apex, peak (mountain peak), and zenith are synonymous.
The term (mountain top) is generally used ...
as well as several radio communications facilities. It is a
composite volcano of
scoria resting on
lava disc and
tuff
Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock cont ...
. The area around Mount Porndon is known as the stony rises. Early settlers used the abundance of rock to build extensive stone fences in the surrounding area.
Description
Mount Porndon is the central higher part of a volcanic complex including
lava
Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...
flows, tuff deposits and
scoria cone
Scoria is a pyroclastic, highly vesicular, dark-colored volcanic rock that was ejected from a volcano as a molten blob and cooled in the air to form discrete grains or clasts.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, eds. (2005) ''G ...
s and
craters. The site covers a broad area including the major elements of
volcanic sequence. Some
basalt
Basalt (; ) is an aphanite, aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the planetary surface, surface of a terrestrial ...
lava flows extend from Mount Porndon forming rough stony rises, some of which reach
Lake Corangamite. The younger of these flows formed an irregular lava disc roughly 3 km in diameter with a distinct and almost continuous perimeter in places forming a rocky wall 10 to 15 meters high. The stony rise flows have been dated at 300,000 years.
Overlying the lava disc is a thin layer of tuff. The main hills and cones were built from scoria eruptions which succeeded the
phreatomagmatic
Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions cont ...
stage after depleted
groundwater
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidate ...
. Small lava flows from some vents beneath the scoria are the last eruptive activity. The central cone of Mount Porndon has a crater 15 m deep and open to the west.
References
*http://www.dpi.vic.gov.au/dpi/vro/coranregn.nsf/pages/corangamite_eruption_points_porndon
{{DEFAULTSORT:Porndon, Mount
Stratovolcanoes
Volcanoes of Victoria (state)
Mountains of Barwon South West (region)