- Slides: 15
Today’s Objective: What Makes Sedimentary Rocks Special? Sedimentary Rocks are one of the three main rock types
A sedimentary rock can form one of three ways: 1. by the deposition of the weathered remains of other rocks 2. by the deposition of the results of biologic activity 3. by precipitation from solution.
• Compaction – is a process that squeezes, or compacts, sediments. • Cementation – “glue” takes place when dissolved minerals are deposited in the tiny spaces among sediments.
• Weathering - is a process in which rocks are physically and chemically broken down by water, air, and living things. • Erosion - involves weathering and the removal of rock. • Deposition - when an agent of erosion – water, wind, ice, or gravity – lose energy, it drops the sediments.
Please add… • Agents of Erosion: Water, wind, ice/glaciers, and gravity
Classification of Sedimentary Rocks • Can be classified into two main groups according to the way they form.
Inorganic Land Derived (AKA) Clastic Sedimentary Rock - composed of weathered bits of rocks And minerals. These rocks are classified by particle size.
EXAMPLES of Inorganic Land Derived Conglomerate Large grain size Shale with Plant Fossils Small grain size
Chemical Sedimentary Rocks – Forms when dissolved minerals precipitate from water solutions. (water usually evaporates or boils) Ex: Limestone & rock salt. Salt Flat
Organically Formed Sedimentary Rocks – Forms when shell fragments are cemented together or when plant remains are compacted into rock. • Ex: Fossiliferious Limestone & Bituminous Coal
Features only found in Sedimentary Rocks 1. The Law of Superpositioning - In undisturbed rocks, the oldest layers are found on the bottom and the youngest at the top.
Please add… • Lithification: Physical and chemical processes that transform sediments into sedimentary rocks (compaction + cementation)
2. Ripple Marks – rock formed along the beach or stream bed. 3. Mud Cracks - formed when wet mud or clay dried and shrank, leaving a rock record of a dry environment. 4. Fossils – traces of remains of ancient life. Trilobite
Where is the oldest layer located on this picture?