User:Awickert/Sandbox

10 things a geologist should know

 * 1) How to identify rocks and minerals, generally well, in outcrop, hand sample, and microscope
 * 2) How to manipulate the stress and strain tensors for a variety of rheologies (because the Earth is messy), and to relate this to faults, folding, seismic waves, and flow, on and within the Earth
 * 3) How to make precise observations and take detailed, useful notes, and how to use these observations to construct sound theories about how things on the Earth generally work.
 * 4) How to locate and orient themselves in the field, with map and compass, or without, during both day and night
 * 5) Relative dating and absolute dating: how they work.
 * 6) The interior structure of the Earth: plate tectonics, mantle convection, geodynamo.
 * 7) How sediments are transported and the geologic record is formed.
 * 8) Enough about natural hazards and climate change to be useful to others who have questions about such issues
 * 9) How to use all details inside a rock (bedding, fossils, foliation, metamorphic phase transitions, sedimentary structures, igneous textures, bulk mineralogy, etc.) to create a combined picture of how that rock was formed and what it says about geological history.
 * 10) A sense of humility that even the best-sounding theory can be utterly destroyed by empirical evidence.

Solar Forcing / Cosmic Rays and Clouds
During the more active phase of the sunspot cycle, the solar wind increases. This modulates the interplanetary magnetic field, which has a role in deflecting cosmic rays. Because the Earth's magnetic field also deflects cosmic rays, the impact of this varies with latitude. The flux variations go from approximately 10% at low latitude to 50% at high latitude, with a reasonable degree of uncertainty.

Cosmic rays are the principle source of ionization in the atmosphere above ~1 km; the lower atmosphere has a large component from radon and other natural background radioactivity. There are several plausible, but unproven, mechanisms where changes in ionization can aid or inhibit the creation of clouds by acting as nucleation sites that impact condensation of water vapor. Because dust and aerosols can also act as nucleation sites, most hypothesized ionization mechanisms are probably only significant in relatively clean air where there are few other nucleating materials. Cloud cover as a whole is responsible for a net of approximately 30 W/m^2 of radiative forcing, so relatively small variations could produce a measurable impact on climate.

This mechanism is an area of active research. One of the complicating factors is that the magnitude and sign of climate forcing varies by cloud type, so the altitude and location of these effects is an important consideration.

Good records of cosmic ray flux are available for over 50 years, but do not show any large trend. The absence of a trend suggests that even if there is a connection between cosmic rays and climate, it is unlikely to play a large role in the warming over the last several decades.

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In geology
In sedimentary geology and geomorphology, sedimentation refers to the deposition of solid particles, or grains. This occurs when the settling velocity of the grains is greater than the upwards velocity on the grains which is induced by a drag force. This occurs:
 * In river deltas, where the river meets the ocean and the flow of water expands in width and depth, and therefore decreases in velocity
 * In the front of glaciers, where

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The Sioux Quartzite is a red to pink Proterozoic quartzite. It is a thick stratigraphic unit (~3000 m ) that crops out in southwestern Minnesota, southeastern and south-central South Dakota, northwestern Iowa, and northeastern Nebraska. It is correlated with other sandstone and quartzite units across Wisconsin (at Rib Mountain, Baraboo, Barron, Waterloo, and Flambeau), southeastern Iowa, southern Nebraska, and north-central New Mexico and southeast-central Arizona (Ortega, Mazatzal, and Deadman Quartzite.

Its age is constrained to be between 2280 ± 110 Ma (mega annum - million years ago) from the Uranium-Lead dating of a rhyolite that underlies it in northwestern Iowa, and 1120 Ma from a Potassium-Argon date of deformation of the Sioux Quartzite in Pipestone, Minnesota. Its age can be better-constrained by extrapolation correlative units to between 1760 ± 10 Ma and 1640 ± 40 Ma. This period in which The Sioux Quartzite and its correlative units were deposited is known as the Baraboo interval, in which high relative sea levels covered a large amount of North America.

The Sioux quartzite was primarily formed by braided river deposits, of quartz arenite composition, with 95% rounded sand-size quartz grains. The rivers are believed to flow southeast, at a relatively shallow gradient. Its basal conglomerate is thought to be braided stream deposits that are more proximal to the source, and there is possible marine influence on the upper part of the unit - this interpretatin is supported by evidence of marine sediments (shales and banded iron formations) atop its correlative unit in Baraboo, Wisconsin. In addition, the unit contains ~1 meter beds of claystone, which are known as Catlinite or Pipestone, because these beds were used by the natives of the area to carve pipe bowls.

The Sioux Quartzite is extremely resistant to erosion, and has formed a topographic high through most of Phanerozoic time. It was only innundated by Phanerozoic seas during the periods of maximum sea level, and subsequent erosion removed these sedimentary units. Today, the only unit to sit atop the Sioux Quartzite is of Cretaceous age. Many present-day outcrops of Sioux Quartzite were exposed by glacial erosion.