Magma of partial melting of the mantle, komatiite and picrite are produced. Magma develops within the mantle or crust where the temperature and pressure conditions favor the molten state. After its formation, magma buoyantly rises toward the Earth's surface. As it migrates through the crust, magma may collect and reside in magma chambers (though recent work suggests that magma may be stored in trans-crustal crystal-rich mush zones rather than dominantly liquid magma chambers ). Magma can remain in a chamber until it cools and crystallizes forming igneous rock, it erupts as a volcano, or moves into another magma chamber.There are two
Boring Lava Field Quaternary, in what is now the Portland area as well as the surrounding area, with a particularly concentrated pocket of activity to the east. Nearly all of these eruptions were confined to single vents or small vent complexes, with the exception of a lava plain southeast of present-day Oregon City. Boring Lava generally consists of flowing lava; only one eruptive deposit contains tuff, ash, and tuff breccia, and one vent to the northeast of the Carver area displayed evidence of explosive eruptions that later became effusive. According to the United States Geological Survey, sometime less than 100,000 years ago, magma