Aftershock — An earthquake which follows a larger earthquake or main shock and originates at or near the focus of the larger earthquake. Generally, major earthquakes are followed by a larger number of aftershocks, decreasing in frequency with time. Albedo — The amount of solar radiation that is reflected back off a surface. Alum — A chemical compound that can be processed from clays. It has been used for industrial purposes e.
Glossary | Resources | Discovering Geology | British Geological Survey (BGS)
Activity increased in the mids after about 50 years of quiescence, and the current eruption, which has been ongoing since January , has included frequent ash plumes and numerous episodes of lava-dome growth and destruction within the m-wide summit caldera. Multiple emissions of steam and gas occur daily, rising generally km above the 5. Larger, more explosive events that generate ashfall in neighboring communities often occur every week. Activity through July was typical of the ongoing eruption with near-constant emissions of water vapor, gas, and minor ash, as well as multiple explosions every week with ash-plumes and incandescent blocks sent down the flanks BGVN This report covers similar activity through February
How Old is the Earth
These are K-Ar data obtained on glauconite, a potassium-bearing clay mineral that forms in some marine sediment. Woodmorappe fails to mention, however, that these data were obtained as part of a controlled experiment to test, on samples of known age, the applicability of the K-Ar method to glauconite and to illite, another clay mineral. He also neglects to mention that most of the 89 K-Ar ages reported in their study agree very well with the expected ages. Evernden and others 43 found that these clay minerals are extremely susceptible to argon loss when heated even slightly, such as occurs when sedimentary rocks are deeply buried.
For a more detailed classification see QAPF diagram. Example of classification Granite is an igneous intrusive rock crystallized at depth , with felsic composition rich in silica and predominately quartz plus potassium-rich feldspar plus sodium-rich plagioclase and phaneritic, subeuhedral texture minerals are visible to the unaided eye and commonly some of them retain original crystallographic shapes. Magma origination The Earth's crust averages about 35 kilometers thick under the continents , but averages only some 7—10 kilometers beneath the oceans. The continental crust is composed primarily of sedimentary rocks resting on a crystalline basement formed of a great variety of metamorphic and igneous rocks, including granulite and granite.