New Zealands Banks Peninsula
History of feature
Banks peninsula is a peninsula of volcanic origin on the east coast, south of Christchurch, on the south island of New Zealand. The banks Peninsula is the most prominent volcanic feature of the South Island. It is approximately 450 sq. miles in area and its highest point is Herbert Peak, at 3,014 ft. It comprises of two extinct volcanoes whose craters have subsequently been enlarged to many times their original size by stream erosion; they were then invaded by the sea during the world-wide rise in sea level beginning about 15,000 years ago. They now form the harbours of Lyttelton and Akaroa. Originally Banks Peninsula was an island, but it became tied to the Canterbury Plains at some late stage in geological history when the growing alluvial plain reached its base. hot spots
Mantle plumes are areas of hot, upwelling mantle. A hot spot develops above the plume. Magma generated by the hot spot rises through the rigid plates of the lithosphere and produces active volcanoes at the Earth's surface. As oceanic volcanoes move away from the hot spot, they cool and subside, producing older islands, atolls, and seamounts. As continental volcanoes move away from the hot spot, they cool, subside, and become extinct. plate techtonics
Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core. The plates act like a hard and rigid shell compared to Earth's mantle. This strong outer layer is called the lithosphere.
Subduction zones, or convergent margins, are one of the three types of plate boundaries. The others are divergent and transform margins. At a divergent margin, two plates are spreading apart, as at seafloor-spreading ridges or continental rift zones such as the East Africa Rift Transform margins mark slip-sliding plates, such as California's San Andreas Fault, where the North America and Pacific plates grind past each other with a mostly horizontal motion.
shiel volcanoes/scoria cone
A shield volcano is a type of volcano usually built almost entirely of fluid magma flows. They are named for their large size and low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid lava they erupt, which travels farther than lava erupted from stratovolcanoes. This results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form. Shield volcanoes contain low-viscosity magma, which gives them flowing mafic lava.
Most of what is currently known about shield volcanic eruptive character has been gleaned from studies done on the volcanoes of Hawaii, By far the most intensively studied of all shields due to their scientific accessibility, and the island lends its name to the slow-moving, effusive eruptions typical of shield volcanism, known as Hawaiian eruptions. These eruptions, the calmest of volcanic events, are characterized by the effusive emission of highly fluid basaltic lavas with low gaseous content. These lavas travel a far greater distance than those of other eruptive types before solidifying, forming extremely wide but relatively thin magmatic sheets often less than 1 m (3.3 ft) thick. Low volumes of such lavas layered over long periods of time are what slowly constructs the characteristically low, broad profile of a mature shield volcano.
Rocks involved
Ignious basalt
Basalt is a dark-coloured, fine-grained, igneous rock composed mainly of plagioclase and pyroxene minerals. It most commonly forms as an extrusive rock, such as a lava flow, but can also form in small intrusive bodies, such as an igneous dike or a thin sill. It has a composition similar to gabbro. The difference between basalt and gabbro is that basalt is a fine-grained rock while gabbro is a coarse-grained rock.
Aggiomentric
Scoria
Scoria is a highly vesicular, dark coloured volcanic rock that may or may not contain crystals. It is typically dark
