why are sands and clay soft?
828414
We are dealing with an illusion caused by grain size and moisture content here.  In fact sand is quite hard because it is made up of individual rock and mineral grains.  Limestone and quartz are pretty hard materials.  If a sand is damp, or has very small rounded grains, it can feel soft to the hand however.\n\nClays on the other hand are soft because they are created by the chemical weathering of other minerals (such as pyroxene or feldspar) and the individual clay units are microscopic in size.  Clays usually contain a high proportion of water in their structure as well (it can be as high as 70%).\n\nWhen a geologist in the field can't make out the whether a rock is a siltstone (clastic) or clay (chemical) because the grain sizes are too small to see, a simple test is to break off a small fragment put it between ones teeth.  If its chewy and soft, its a clay.  If its hard and gritty, its a silt. \n(Warning - experts only folks.  Some rocks contain poisonous minerals so don't go around randomly tasting rocks.)
303122
"Sandy Loam Soil"  is almost pure sand! anything else you might like to know would be listed under "soil science" enjoy!!!
158901
THe sand that the Tower of Pisa was built on is very soft and the weight of the building has caused the ground underneath to give-way.
1170123
They convert inorganic material to organic ones to make the soil fartile. This is done due to their living and it also helps in living the plants... both way benefecial :)
191382
Yea, the first answer is right.  Among many other factors, soils are made up of parent material that has decomposed.  It mostly depends on what kind of rock they came from.
217588
Liquefaction occurs when the structure of a loose, saturated sand breaks down due to some rapidly applied loading. As the structure breaks down, the loosely-packed individual soil particles attempt to move into a denser configuration. In an earthquake, however, there is not enough time for the water in the pores of the soil to be squeezed out. Instead, the water is "trapped" and prevents the soil particles from moving closer together. This is accompanied by an increase in water pressure which reduces the contact forces between the individual soil particles, thereby softening and weakening the soil deposit.  \n      Observe how small the contact forces are because of the high water pressure. In an extreme case, the porewater pressure may become so high that many of the soil particles lose contact with each other. In such cases, the soil will have very little strength, and will behave more like a liquid than a solid - hence, the name "liquefaction".
468095
In general, the more clay in the soil, the higher the cation exchange capacity, the greater the rates of expansion (i.e. greater rates of saturation).\n\nMontmorillonite would expand quikcer because it has the highest cation exchange capacity of all the 2:1 lattice clays.  This higher cation exchange capacity allows for the clay minerals to bond quickly with water or with base cations present, therefore expanding quicker than vermiculite which has a lower cation exchange capacity. \n\nHowever, a vermiculite that is not saturated with base cations will expand quicker than a montmorillonite that is saturated with base cations.  If neither is saturated, the montmorillonite will expand quicker because of its greater cation exchange capacity.\n\nMontmorillonite clays mixed in with soil will be far more fertile than vermiculite mixed in with the soil.  However humus has an even higher cation exchange capacity than both montmorillonite and vermiculite.
721095
Clay because it will just go down to the bottom of the river without causing environmental damage.
995527
CLAY- Earth material, chiefly made up of Al2 O3.2SiO2.2H2O,(Aluminium oxide/silicon dioxide/hydrogen oxide ?) forming a paste when wet but turning very hard under the operation of heat.\nSAND- Loose material formed of small but clearly separate round grains, chiefly of QUARTZ, from about 0.1 to 1 mm, across, produced by the rubbing away of solid stone, and put down in stretches by water or formed into masses by wind.
1148422
Think about sand in a bucket with holes in the bottom.  The sand will go through the holes because its grains are smaller.  In the same way, the smaller pieces of coffee bean can squeeze in and around the larger beans and settle to the bottom.  This principal is commonly used by geotechnical engineers to determine particle sizes of soil.
250052
soil is composed of mineral and organic matter.\nmineral components are small particles of rock, derived from the underlying rocks, and brought in from nearby areas by the rivers\nthe organic matter is vegatable and animal remains in a state of decomposition ( called humus)\n\nThe texture is dependant on the size of mineral particles, and  corresponding airspaces, clay being the smallest, sand being largest.
661467
To my knowledge, apart from tennis courts and similar sports areas, this isn't done. For walkways and foundations, the sand is condensed using water and/or mechanical force. Sand ways usually are built where 100% sealing of the ground is prohibited, or where it is "green" not to use any kind of stone tiles or tarmac. In either case, no chemicals would be added to stabilize the sand.\n\nBelow stone tiles for walkways sometimes meagre concrete is used.
465216
Well if you had been paying attention, Mythbusters proved that there is not such thing as quick sand. They tried their best but it just doesn't exist.\n\nSeems like the principle of a body being lifted up by a force equal to the weight of the material displaced keeps getting in the way. Sand and water on a cubic foot basis weights much more than either the donkey's or mule's average weight per cubic foot.
1141432
Soft --- Ice Cream, my pillow, matress, gum, tacos, skin\n\nHard --- Hardcover books, rocks, the ground, my brothers head lol.\n\n\ngood enouth answers 4 yea?
492924
i'm not exactly sure, but i would think that it would depend on the soil composition.  after all a fine clay has much different properties than a sandy or rocky soil
1178623
solid's particles are compact, while on liquids they are loose but gas' are the most loose (more distances with each other)
320640
Bentonite is a type of clay that has some specific features that make it useful in many different industries.  Its structure is such that it forms "platelets" of a very small particle size, which provide an enormous amount of surface area.  This surface is very chemically active and highly receptive to water.  When water permeates a Bentonite clay, the individual platelets chemically bond to one another and swell as a mass, forming a virtually water-tight seal.  This is why Bentonite clays are often used to waterproof foundation walls, and also as a sort of grout that can be pumped or sprayed into/around structures that will be exposed to water (i.e. pilings, pond linings, retention basins, etc) in order to prevent water intrusion.  It can also be mixed with soil to create a harder, more impervious compacted soil which provides a better base for construction. Bentonite clays are also widely used in paints and other coatings as viscosity modifiers, since the chemical/mechanical activity of wetted and dispersed Bentonites is to "swell" and thereby provide a thicker viscosity to otherwise "thin" materials.  It's frequently a component of fingernail lacquers, which require a fairly high viscosity for ease of application.