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In USDA soil taxonomy, andisols are soils formed in volcanic ash and defined as soils containing high proportions of glass and amorphous colloidal materials, including allophane, imogolite and ferrihydrite. [1] In the World Reference Base for Soil Resources (WRB), andisols are known as Andosols. [2]
Andosols are soils found in volcanic areas formed in volcanic tephra. In some cases Andosols can also be found outside active volcanic areas. [1] Andosols cover an estimated 1–2% of Earth's ice-free land surface. Andosols are a Reference Soil Group of the World Reference Base for Soil Resources (WRB). [2]
Volcanic ash's primary use is that of a soil enricher. Once the minerals in ash are washed into the soil by rain or other natural processes, it mixes with the soil and forms an andisol layer. This layer is highly rich in nutrients and is very good for agricultural use; the presence of lush forests on volcanic islands is often as a result of ...
Some scientists have suspected a volcanic winter resulting from the eruption was a big enough shift to wipe out most early humans due to genetic evidence suggesting a steep drop in the human ...
A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice, typically a volcanic cone or mountain. [2] [22]
Other earth materials include soil blocks typically stabilized with a cement additive and produced with forms or compression. Rammed Earth consists of walls made from moist, sandy soil, or stabilized soil, which is tamped into form work. Walls are a minimum of 12″ thick. Soils should contain about 30% clay and 70% sand. [4]
This page was last edited on 29 July 2007, at 20:00 (UTC).; Text is available under the Creative Commons Attribution-ShareAlike 4.0 License; additional terms may ...
The Trans-Mexican Volcanic Belt has many endemic species, including the Transvolcanic jay (Aphelocoma ultramarina). [4] Volcanic ash make soils in the region very fertile, which (especially coupled with elevation making tropical climate milder) has led to high human population densities in the belt that now sometimes strain the environment.