Search results
Results from the WOW.Com Content Network
Shield volcanoes are large, slow forming volcanoes [6] that erupt fluid basaltic magma that cools to form the extrusive rock basalt.Basalt is composed of minerals readily available in the planet's crust, including feldspars and pyroxenes.
However, extrusion at mid-ocean ridges is relatively steady, while extrusion of flood basalts is highly episodic. Flood basalts create new continental crust at a rate of 0.1 to 8 cubic kilometers (0.02 to 2 cu mi) per year, while the eruptions that form oceanic plateaus produce 2 to 20 cubic kilometers (0.5 to 5 cu mi) of crust per year.
There are three models that help explain this emplacement: wedge extrusion, channel flow, and tectonic wedging. The wedge extrusion and channel flow models work under the assumption that the STD is a low angle normal fault, while the tectonic wedge model works as if the STD is a thrust fault. [5] Figure 2: Wedge extrusion model.
In 1992, Coffin and Eldholm initially defined the term "large igneous province" as representing a variety of mafic igneous provinces with areal extent greater than 100,000 km 2 that represented "massive crustal emplacements of predominantly mafic (magnesium- and iron-rich) extrusive and intrusive rock, and originated via processes other than 'normal' seafloor spreading."
In geology, an igneous intrusion (or intrusive body [1] or simply intrusion [2]) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth.
The collision-extrusion model argues that the opening of the South China Sea Basin is related to the collision of the Indian Plate and the Eurasian Plate. The Borneo and Indochina plate are still considered as a single block and attached to each other. When India collided with Eurasia, part of the continent was pushed towards the southeast.
Pillow lavas are lavas that contain characteristic pillow-shaped structures that are attributed to the extrusion of the lava underwater, or subaqueous extrusion. Pillow lavas in volcanic rock are characterized by thick sequences of discontinuous pillow-shaped masses, commonly up to one meter in diameter.
Hot extrusion is a hot working process, which means it is done above the material's recrystallization temperature to keep the material from work hardening and to make it easier to push the material through the die. Most hot extrusions are done on horizontal hydraulic presses that range from 230 to 11,000 metric tons (250 to 12,130 short tons ...