Geology Exam Ch. 6,7,9

What is the difference between a breccia and conglomerate? In what environment do you find each type?

Breccia- Angular Particles Conglomerate- Rounded Particles They exist in a water flowing moist environment that rounds them.

Explain how carbonates can be formed organically(biochemically) and non-organically. List some examples of each.

Carbonates are formed from CaCO3 (limestone) Organically- Percipitated through actions of organisms. Inorganic- precipitated directly as the result.

Explain how chert is often formed?

Chert is formed when a fine-grained sedimentary rock is formed almost entirely of silica and formed from inorganic precipitation where underground water replaced part of the original rock

List from smallest to largest: What is the difference among a sandstone, siltstone and shale?

Clay, Silt, Sand, Pebble, Cobble Sandstone- Formed by the cementation of sand grains Shale- A fine-grained sedimentary rock notable for its ability to split into layers. Siltstone- Consisting of consolidated silt.

Where do you commonly find sandstone? What is the difference between a quartz sandstone and an arkose.

On the seafloor Quartz sandstone is 90% quartz grains. Arkose is 25% feldspar in its grains.

How are oolitic, tufa and travertine formed?

Oolitic- Formed by the cementation of small spheres of calcite inorganically. Tufa- a percipitated solution in the water of continental spring/lake percolating water.

What are the 3 main types of sedimentary rocks?

Gravel, Sand, Clay

How does current strength and weathering affect particles? What is the difference between well-sorted and poorly sorted deposits? Why are some rocks rounded?

1) It affects the deposition and the lithification 2) Well-sorted deposits are preserved better and cemented better than poorly sorted deposits 3) Some rocks are rounded because they are in a water source of some form and smaller sands and rocks grind it down.

What is bedding? What is a bedding plane?

Bedding- A series of visible layers within rock. Bedding Plane- A nearly flat surface of deposition separating two layers of rock.

What are the effects of heat, pressure, and cementation when sediments undergo lithification? a) Name two types of "natural cements" b) Which type is commonly used in concrete to make sidewalks and buildings? c) What type of cement do you think would more easily erode in an acidic environment?

Compaction a) Breccia & Conglomerate b) Sandstone c) Graywacke

What are the differences among a shale, silstone, claystone and mudstone. What does fissile mean?

Differences: Shale- fine-grained sedimentary rock that is very fissile. Siltstone- A rock that consists mostly of silt grains Claystone- rock composed of clay-sized particles but lacks fissility of shale. Mudstone- contains both silt and clay, the grain size and smooth feel of shale but not the as sleek and shiny. Fissile- A sedimentary rocks ability to split into layers.

What is formation and Contact?

Formation- A body of rock considerable thickness that is large enough to be mappable, and with characteristics . Contact- The boundary surface between two different rock types or ages of rocks.

Explain how evaporites are formed?

Evaporites are formed from the evaporation of seawater or a saline lake. Ex: Gypsum, Salt

List 3 different ways fossils are formed

Petrified Molds Trace

How can you determine the direction of current by studying cross-beds and ripple marks?

The way the bedding settles and the direction the sand usually settles and on what side tells the direction of current.

How do cross-bedding, graded bedding, ripples and mudcracks form?

They form when sediments are deposited and are originally deposited as horizontal layers.

Consider a stream flowing from a mountains area downhill to a flat flood plain and then onto the coastline and eventually into ocean. a)In what area are you most likely to find large, angular rocks? b) In what area are you most likely to find breccia rocks formed? c) In what area are you most likely to find sand-sized particles? d) In what area are you most likely to find only clay and silt-sized particles?

a) The mountains b) Mountain Area and Coastline c) Coastline and Ocean d) Ocean