Rocks, Rocks, and more Rocks - Sedimentary Sedimentary rocks are classified by the types of sediments that make up the rock
What are sediments? • Definition: • Small, solid pieces of material that come from rocks or living things like bones, leaves, stems, etc
There are 4 main processes needed to form sedimentary rock: Step 1: EROSION (wash away) Forces of running water, wind, or ice that loosen & carry away fragments of rock Can you see the sediment moving in the water? Have you ever seen sediments being moved during a hard rain?
There are 4 main processes needed to form sedimentary rock: Step 2: DEPOSITION (drop down) Sediments settle out of the water or wind carrying them & settle to the bottom of a lake or ocean. Sediments move down the sloped land & settle at the bottom. Over time these sediments layer up.
There are 4 main processes needed to form sedimentary rock: Step 3: COMPACTION (smashed together) Process that presses sediments together. Thick layers of sediment build up over time & weigh down the layers compacting them.
There are 4 main processes needed to form sedimentary rock: Step 4: CEMENTATION (glued together) Dissolved minerals seep into spaces between particles (sediments) & then crystallize as they harden.
3 Types of Sedimentary Rocks • Clastic Sedimentary Rock Made from fragments that are squeezed together
Comparing 2 Clastic Sedimentary Rocks: Shale Forms from mud - tiny clay particles, quartz & calcite; Sandstone Forms from sand on beaches, ocean floor, river beds, etc
Comparing 2 more… Conglomerate From rounded sediments Breccia From larger, sharp fragments
3 Types of Sedimentary Rocks 2. Organic Sedimentary Rock Forms where the remains of plants & animals are deposited in thick layers
Comparing 2 Organic Sedimentary Rocks Coal From swamp plants buried in water for millions of years (plants peat coal) Limestone Forms from hard shells w/calcite from seashells, coral, clams, oysters or skeletons that pile up on the ocean floor for millions of years slowly changing the sediment to limestone
Use for coal & a location of limestone… Coal Limestone *** Plant Bowen is a power plant that uses coal. Has anyone seen this before? It’s not too far away! Limestone in England where there was once H2O covering the land.
3 Types of Sedimentary Rock 3. Chemical Sedimentary Rock Forms when minerals that have been dissolved in a solution with water, crystallize
Examples of Chemical Sedimentary Rock Limestone *** Another form of limestone forms from calcite in seas, lakes & underground caves – forms caverns & sinkholes in the ground when it is eroded by ground water Rock Salt Forms from halite when evaporation leaves salt behind
Comparing 2 Chemical Sedimentary Rocks Limestone *** Rock Salt 600 million year old rock salt being mined in the Himalayan Crystal Rock Mine. Ruby Falls cave is made of limestone! How did the cave form?
Uses: What things have been made from Sedimentary Rock? • Flint: Arrowheads • Sandstone: THE WHITE HOUSE • Limestone: Blocks & slabs for building, making cement & steel, flooring
Possibly the coolest thing about Sedimentary Rock… FOSSILS are always found in Sedimentary Rock ONLY! Why???
Fossils are the signs of the plants & animals that have lived on Earth for millions of years…sometimes we see the whole creature or actual parts of the plant…sometimes we see evidence that a creature lived…
“Law of Superposition”states that new sediment layers are added on top of older rock layers on the bottom
Oldest: FNext: EWhat happened with layer D?Then: C, B, AWhat is happening over & on top of layer A? Law of Superposition states that older rock layers are at the bottom. If there is tectonic plate movement or if an Igneous rock intrusion breaks through the rock layers, then the order is disrupted.
Some great resources for Sedimentary Rocks & more:Additional resources can be found on my webpage. You can also use the internet to search the topic you are interest in. Lots of great stuff out there! Geology http://www.kidsgeo.com/geology-for-kids/0027-sedimentary-rocks.php More Geology http://www.rocksforkids.com/RFK/howrocks.html Science Articles http://www.buzzle.com/articles/rocks-and-minerals-for-kids.html Sedimentary Rocks http://www.rocksforkids.com/R&M/sedimentary.htm