Misema Caldera | |
|---|---|
 Map of the Blake River Megacaldera Complex. Misema Caldera is highlighted in red. | |
| Location | Ontario-Quebec, Canada |
| Range | Canadian Shield |
| Age | 2,704-2,707 MYA |
| Volcanic arc/belt | Blake River Megacaldera Complex |
The Misema Caldera is a 2,704-2,707 million year old caldera in Ontario and Quebec, Canada.
It is the caldera that forms the Blake River Megacaldera Complex [1] and has a diameter of 40-80 kilometres.
The caldera is also a coalescence of at least two large mafic shield volcanoes that formed more than 2703 million years ago. [2] The rim of the Misema Caldera contains a 10-15 kilometre wide inner and outer ring zone, in which many mafic ring dike complexes and subaqueous pyroclastic sediments are detected.
The mafic ring dike structures may be deeper level expressions of summit calderas related to a shield volcano phase while the pyroclastic fragments could either be associated with satellite cones or the result of Misema caldera collapse. [2]
Misema Caldera is the oldest and largest caldera associated with the Blake River Megacaldera Complex and is comparable in size to Lake Toba caldera in Indonesia. [2]
A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is gone. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur each century, the formation of a caldera is a rare event, occurring only a few times per century. Only seven caldera-forming collapses are known to have occurred between 1911 and 2016. More recently, a caldera collapse occurred at Kīlauea, Hawaii in 2018.
The Taupō Volcanic Zone (TVZ) is a volcanic area in the North Island of New Zealand that has been active for the past two million years and is still highly active. Mount Ruapehu marks its south-western end and the zone runs north-eastward through the Taupō and Rotorua areas and offshore into the Bay of Plenty. It is part of the larger Central Volcanic Region that extends further westward through the western Bay of Plenty to the eastern side of the Coromandel Peninsula and has been active for four million years. At Taupō the rift volcanic zone is widening east–west at the rate of about 8 mm per year while at Mount Ruapehu it is only 2–4 mm per year but this increases at the north eastern end at the Bay of Plenty coast to 10–15 mm per year. It is named after Lake Taupō, the flooded caldera of the largest volcano in the zone, the Taupō Volcano and contains a large central volcanic plateau as well as other landforms associated with its containing tectonic intra-arc continental Taupō Rift.
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The Blake River Megacaldera Complex is a giant subaqueous caldera cluster or a nested caldera system that spans across the Ontario–Quebec border in Canada.
The New Senator Caldera is a large Archean caldera complex within the heart of the Blake River Megacaldera Complex, Quebec, Canada. It has a diameter of 15-30 kilometers and is made of thick massive mafic sequences. The caldera complex has inferred to be a subaqueous lava lake during the early stages of the caldera's development. Gabbro sills represent lava lakes, which are common in mafic summit calderas. These subaqueous lava lakes are large units with a change in grain size from coarse to fine grained and a hyaloclastite top. The Kiwanis (Norands) intrusion, a high-level synvolcanic magma chamber, intrudes felsic rocks, and is in turn cross-cut by basaltic dikes and sills.
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