This is an Earthcache, which does not have a physical container, but provides a learning exercise and a chance to show that knowledge in this setting. Please send me the answers to the questions below to validate your log.
Welcome to Galveston Beach.
Galveston Beach is known as a great vacation spot on the Gulf. It's sand is soft and beautiful. This Earthcache will hopefully teach you a little on sand and its sizes.
Definition: Sand is a naturally occurring granular material composed of finely divided rock and mineral particles. It is defined by size, being finer than gravel and coarser than silt.
What is sand?
Sand is a loose granular material blanketing the beaches, riverbeds and deserts. In different areas sand has different components which makes the sand white, black, green or pink in color.
Sand is mostly composed of silicon dioxide in the form of quartz. Quartz is hard and does not decompose easily.
The Earth's landmasses is composed of rocks and minerals, including quartz, feldspar and mica. Weathering processes like wind, rain and freeze/thaw cycles break these rocks and minerals down into smaller grains.
Unlike other minerals quartz is hard, insoluble in water and won't decompose easily from weathering processes. Streams, rivers and wind transport quartz particles to the seashore where the quartz accumulates as light-colored Beach Sand.
Sand comes in basically 5 sizes.
1) Very Coarse Sand 0.039 - 0.079 inches
2) Coarse Sand. 0.020 - 0.039 inches
3) Medium Sand. 0.010 - 0.020 inches
4) Fine Sand 0.0049 - 0.010 inches
5) Very Fine Sand 0.0025 - 0.0049 inches
Sand is measured using the Wentworth scale.
Sand Gauge
Transport Distance
The shape of the sand depends on the distance that it is transported. Longer distances bring smoother shapes, like to the right of the table.
Grain Composition
Any type of rock on the surface of the Earth's crust can give rise to sand.
A grain of sand may be a fragment of rock (lithoclast), mineral (mineraloclasts) or an organism (bioclast).
The color that the sands present is directly related to this composition.
The most common are light-colored quartzites, which present quartz (the most abundant mineral in nature) as the predominant component. It has great resistance to the actions of external agents.
in some sands, there may also be other minerals such as more or less altered felsdspars, micas among others.
However, there are sands that are mostly composed of ferromagnesian minerals, such as olivines, pyroxenes, amphiboles, and therefore have a dark color, or by lithic components (fragments of limestone, basalt, etc.)
The sands originated in volcanic materials are usually dark because of the presence of ferromagnesian silicates typical of basaltic rocks, especially pyroxenes, amphiboles and olivine, black oxides (magnetite and ilmenite or even lithoclasts)
Siliceous sands are white, when pure, as are calcareous sands
The calcareous sands, as well as those whose constitution enters carbonate shells or fragments of these, make effervescence with the hydrochloric acid, this test is very used in the field for being fast and allow to evaluate qualitatively the presence or absence of these components.
Sands rich in organic matter or in manganese compounds are black in color
The iron compounds give the sands a yellowish or greenish color
Logging Requirements
Go to the location listed and observe the sand. Send me a description, including the grain size, shape, color and composition.
Feel free to post a picture at GZ, but it is not required.
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