Geological Sciences

Sedimentary Rocks

Photo Gallery


Web Links for Sedimentary Rocks USGS on Sedimentary Rocks Sedimentary Rocks for Teachers Introduction to Sedimentary Rocks Atlas of Sedimentary Rocks	Sedimentary rocks form some of the most beautiful landscapes on Earth. These sedimentary rocks are exposed in Zion National Park, Utah.

Sedimentary rocks require a source area where weathering and erosion are producing sediment. High areas such as Banner Peak in the Sierra Nevada Mountains create sediment which is be transported to a site of deposition as close as Garnet Lake shown here or as distant as the Pacific Ocean..	Sediment may be transported by water, wind, or glaciers. The murky color of the San Gabriel River is caused by stream sediment that is being stirred up by gold miners. The students shown here are crossing the river on a field trip on the East Fork of the San Gabriel River.

A large amount of sediment ultimately reaches the ocean and may be picked up by currents and transported long distances before it is deposited. This photo taken from the Pacific Palisades shows sand accumulating behinds rock groins as the sand is transported south around Santa Monica Bay.	Sediment may be discharged directly from seacliffs and landslides into the ocean. The sediment in the ocean at this location is derived from erosion of the Portuguese Bend landslide.

One of the wonderful things about sediment and sedimentary rocks is that they tell stories about the geological past. The lichen-covered quartzite cobbles shown here are found on the south coast of South Africa. These cobbles were deposited in a rift valley that formed as South America moved away from Africa.	Erosion of pre-existing rocks is not the only origin of sediment. Sediment may have a biological or chemical origin. Shell fragments such as these are often found on beaches in tropical regions.

The De Chelley Sandstone forms the massive cliffs of Canyon de Chelley National Monument. These rocks were deposited in an arid, subtropical area during Triassic time.	The sediment-laden San Juan River carved the Goosenecks into the Pennsylvanian Hermosa Formation. You may visit this site at Goosenecks of the San Juan State Park near Mexican Hat, Utah.

The mesas and buttes carved into the Permian Cutler Formation of Monument Valley, Arizona form some of the most beautiful scenes in western United States.	The rocks of Checkerboard Mesa in Zion National Park show cross bedding formed in sand dunes approximately 200 million years ago. Frost wedging has exaggerated the cross bedding on this northern face of Checkerboard Mesa, Utah.

The rocks at the bottom of the Grand Canyon are 1,700 million years old and represent the roots of an ancient mountain range. There is an erosional gap between these ancient rocks and the 1,250 million year old Bass Formation. This 450 million year gap in the geological record is only one of numerous unconformities in the Grand Canyon.	These Cal State LA General Education students hiked to the Tonto Platform an back over Thanksgiving vacation.

These sandstones and siltstones are exposed on the north coast of Australia's scenic Kimberly Plateau. These rocks are 1,800 million years old and in most areas remain horizontal in spite of all the geological events that have occurred in that long period. However, faults in the sedimentary basin produced local submarine topography and tilting of rock strata. Soft sediment deformation combined with the tectonic event to produce this outcrop.	Sedimentary strata are generally deposited in a horizontal or nearly horizontal position. Strata not in a horizontal position are generally affected by tectonic processes. These steeply-dipping strata were originally deposited in a marine environment. They are now over 18,000 feet above sealevel on the south flank of Denali, Alaska.

The Permian Dwyka Tillite of South Africa was deposited by a glacier on the continent of Gondwana. Note the deep groves carved into the sediment by rocks entrained in the base of the glacier.	Tillite such as this can be found in Antarctica, South America, India, and Africa. The rock shown above in a black matrix is a dropstone that fell to the seafloor from a melting iceberg during the Permian.

Native Americans have used sedimentary rocks for building stones for over a thousands years. Mesa Verde, Colorado provides an excellent example of the high quality of the architects and builders who constructed this cliff dwelling approximately 1,000 years ago.	Sedimentary rocks provide a strong foundation for large dams along the Colorado River. The Glen Canyon Dam of Arizona is shown here.

Does Earth Science look interesting to you? Perhaps you would like to major in Geology or Natural Science. Maybe a General Education course in geology would appeal to you. Here are two links that you should explore. Be an Earth Scientist Geology General Education Courses Return to Photo Gallery index page.
TOP\| \|Home\|

|Home|