6.1 Sedimentary and Metamorphic Rock Flashcards
What is erosion?
The removal and movement of surface materials from one area to another. The four main agents of erosion are wind, moving water, gravity, and glaciers. Materials are almost always eroded downhill.
When does deposition occur?
Occurs when sediments are laid down on the ground or sink to the bottom of bodies of water.
What is deposition?
Sediments are deposited when transport stops. Particles then settle out, forming layers of sediment.
How does deposition vary with wind, water, and glaciers?
With wind and water, different sized particles are settled into layers because both water and wind can be slow and fast moving. Glacier deposits are not sorted because they move materials with equal ease.
What is burial?
Most sediments are deposited in depressions called sedimentary basins which contain layers of sediment that are more than 8 km thick. More layers are deposited and lithification takes place due to increasing pressure and temperature.
How does lithification begin? What are found in the layers of sedimentary rocks?
It begins with compaction. The weight of overlying sediments forces the layers closer together causing the physical change.
Groundwater, oil, and natural gas and commonly found in these spaces.
When does cementation happen?
When sediments that are buried 3 to 4 km thick experience temperatures that are high enough to start chemical and mineral changes.
What is cementation?
Occurs when mineral growth cements sediment grains together into solid rock.
Describe the two types of cementation.
First type- occurs when new minerals such as calcite or iron oxide grows between mineral grains as dissolved minerals precipitate out of groundwater.
Second type- occurs when existing mineral grains grow larger as more of the same mineral precipitate from groundwater and crystallize around them.
What is a primary feature of sedimentary rock?
Horizontal layering called bedding.
How thick can bedding be?
Can be anywhere from a millimetre of shale or sandstone to several meters.
What is graded bedding?
When particle sizes become heavier/coarser towards the bottom.
What are bedding layers observed in marine sedimentary rock created by?
Underwater landslides
What is cross-bedding formed from?
As inclined layers of sediment move foreward across a horizontal surface.
What are some examples of small-scale cross-bedding?
Sandy beaches and sandbars in streams
