Formation of Sedimentary Rocks

Formation of Sedimentary Rocks

• Sedimentary rocks form in layers over millions of years, similar to the pages of a book.
• Each layer is formed through the compression of sand and mud at the bottom of lakes and oceans.
• The pressure from the weight of the layers causes the sand and mud to turn into sedimentary rocks.

Characteristics of Sedimentary Rocks

• Sedimentary rocks display distinct layers or stripes, which may be different colors.
• Newer layers are found at the top of the sequence, while the oldest layers are at the bottom.
• Scientists can determine the relative age of rocks by examining their position in the sequence.

Fossils in Sedimentary Rocks

• Fossils are formed when ancient living organisms die and become preserved in sedimentary rocks.
• Fossils provide clues about the age of the rocks in which they are found.
• The presence and location of certain fossil types indicate the order in which rock layers were formed.
• Fossils in the bottom layers are very different from organisms alive today, and become more familiar as you move up to younger rock layers.

Environmental Clues from Fossils

• Fossils can reveal information about the environment in the past, such as the type of environment, food sources, and more.
• Fossils found in a particular area can indicate what the environment was like in the past, such as whether it was a desert or ocean.

Forces and Change

• Earthquakes and tectonic plate movement can cause rock layers to change, disturbing their original order.
• Pressure and temperature can cause rock layers to bend or fold over.
• Scientists can determine the original order of the layers by comparing disturbed rock layers with undisturbed layers.