Formation of Sedimentary Rocks Section 6.1 Pages 134-140

Weathering: Chemical and Physical A reaction has occurred The minerals have been dissolved and changed as rain falls on the rock Not all minerals can undergo chemical change (resistant) Physical Broken down physically by water The minerals keep their same chemical composition

Erosion Wind Moving water Gravity Glaciers Moving rock from one location to another Most movement is down hill (gravity)

Deposition The process in which sediments come to rest in a location Either settling at the bottom of a body of water or on the ground The sediments form layers These layers have the largest sediments at the bottom and the smallest sediments at the top

Energy of Transporting Agents Fast moving water can move all sizes of sediments whereas slow moving water is limited to smaller sizes Larger sediments settle out sooner than smaller sediments (going from largest to smallest)

Energy of Transporting Agents Sediments moved by water create distinct sedimentary layers Wind has the same ability, but is limited to smaller sediments

Energy of Transporting Agents The movement of glaciers and landslides produce a jumble of sediments The sediments are not separated into layers that are distinct Glaciers move all types of sediments at the same rate and do not separate them into different types

Lithification Sediments for the most part find their final deposition in low areas of the Earth including valleys and ocean basins Lithification is the process by which sediments in deeper layers get subjected to higher pressure and heat leading to the formation of rock

Compaction The first step of lithification The more layers that form on top the more the lower layers become compressed (physical change) Mud can compact much more than sand as sand contains quarts which cannot be compacted Sand therefore has spaces which allows for groundwater, oil and natural gases to fill these gaps

Cementation The process by which minerals in aqueous form (minerals dissolved in ground water) turn to solid The gaps are filled with solids which glues the sediments to one another

Sedimentary features The history of how the rocks formed

Bedding The horizontal layering of sedimentary rocks. The thickness of the layers depends on how they were deposited. The thickness can range from only a few millimeters to several meters thick Layers are typically deposited by wind and water

Bedding There are 2 different types of bedding based on the transport of sediments The grain size and material content can vary and depend on many factors

Graded bedding In this type of bedding the particle size becomes increasingly finer This can be seen in ocean sediments where the larger heaver sediments sink faster and the lighter finer sediments sink slower

Cross-bedding The sediments are deposited on horizontal surfaces Sometimes these sediments solidify producing miniature hills and valleys effect on a horizontal surfaces

Ripple Marks Formed when water or wind movement creates small ridges of sediment Symmetrical and asymmetrical ripple marks can be formed by these movements Symmetrical means the movements are back and forth Asymmetrical means the movement is in one direction