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Spheroidal weathering of a dolerite dyke, Pilbara, Western Australia. Spheroidal weathering is a form of chemical weathering that affects jointed bedrock and results in the formation of concentric or spherical layers of highly decayed rock within weathered bedrock that is known as saprolite.
Orthogonal joint sets quite often result in the formation of rock formations that are comparable in size and shape to the blocks shown in pictures of the alleged megaliths. [8] [9] It is quite common for spheroidal weathering, a form of chemical weathering, to occur as groundwater circulates through orthogonal joint sets in the near-surface. [10]
Spheroidal weathering of exposed sections of the dykes has focussed on cooling joints present within the body of intrusive rock. Radiometric dating of the dykes has returned ages of around 52 million years for their emplacement though an older age of around 61 million years has also been suggested by measurements.
Later hydrothermal vein activity along fault and shear zones within the Butte quartz monzonite and its contact with adjacent rocks, resulted in major ore deposits of lead, zinc, and silver. [2] [3] The Boulder Batholith was named for the prominent rounded boulders that typify its landscape, the result of spheroidal weathering of fractured ...
These cover rocks have since been eroded away. Weathering along joints produced the rounded boulders and other unusual rock formations that characterize the Granite Dells. This process is called spheroidal weathering, and is common in granitic terrains. [5]
Physical weathering, also called mechanical weathering or disaggregation, is the class of processes that causes the disintegration of rocks without chemical change. Physical weathering involves the breakdown of rocks into smaller fragments through processes such as expansion and contraction, mainly due to temperature changes.
Rocking stones (also known as logan stones or logans) are large stones that are so finely balanced that the application of just a small force causes them to rock. Typically, rocking stones are residual corestones formed initially by spheroidal weathering and have later been exposed by erosion or glacial erratics left by retreating glaciers.
The natural processes of weathering and erosion have created the various shapes of the boulders. Some of the boulders are naturally but precariously balanced atop one another or on larger rock formations, while others have been split cleanly down the middle by natural forces. The boulders are situated in a wide and shallow desert valley, and ...