sedimentary rocks

sediments

Sandstone is one of the common types of sedimentary rocks that form from sediments. There are many other types. Sediments may include: fragments of other rocks that often have been worn down into small pieces, such as sand, silt, or clay. organic materials, or the remains of once-living organisms. chemical precipitates, which are materials that get left behind after the water evaporates from a solution. Rocks at the surface undergo mechanical and chemical weathering. These physical and chemical processes break rock into smaller pieces. Mechanical weathering simply breaks the rocks apart. Chemical weathering dissolves the less stable minerals. These original elements of the minerals end up in solution and new minerals may form. Sediments are removed and transported by water, wind, ice, or gravity in a process called erosion (Figure 1.1). Much more information about weathering and erosion can be found in the chapter Surface Processes and Landforms. Streams carry huge amounts of sediment (Figure 1.2). The more energy the water has, the larger the particle it can carry. A rushing river on a steep slope might be able to carry boulders. As this stream slows down, it no longer has the energy to carry large sediments and will drop them. A slower moving stream will only carry smaller particles. Water erodes the land surface in Alaskas Valley of Ten Thousand Smokes. Sediments are deposited on beaches and deserts, at the bottom of oceans, and in lakes, ponds, rivers, marshes, and swamps. Landslides drop large piles of sediment. Glaciers leave large piles of sediments, too. Wind can only transport sand and smaller particles. The type of sediment that is deposited will determine the type of sedimentary rock that can form. Different colors of sedimentary rock are determined by the environment where they are deposited. Red rocks form where oxygen is present. Darker sediments form when the environment is oxygen poor. Click image to the left or use the URL below. URL:

textbook_image

textbook_image

instructional diagrams

No diagram descriptions associated with this lesson

questions

sedimentary rocks are made from

a) fragments of other rocks

b) organic materials

c) chemical precipitates

-->  d) all of the above

which describes mechanical weathering?

a) precipitation that creates minerals.

-->  b) breaking minerals and rocks into smaller pieces.

c) removal of minerals and rocks by water, wind, ice or gravity.

d) dissolution of less stable minerals and rocks.

darker sediments form when the environment is oxygen rich.

a) true

-->  b) false

red rocks are formed when this element is present.

a) nitrogen

b) carbon

c) silica

-->  d) oxygen

organic materials are made from the remains of once-living organisms.

-->  a) true

b) false

erosion is the process in which sediments are removed and transported by water, wind, ice, or gravity.

-->  a) true

b) false

streams erode sediments in this way

-->  a) larger sediments in mountain areas and smaller sediments in flatter regions.

b) smaller sediments in mountain areas and larger sediments in flatter regions.

c) larger sediments were streams move slowly and smaller sediments where they move rapidly.

d) none of the above

landslides dropping large piles of sediment due to

a) wind

b) ice

-->  c) gravity

d) water

chemical precipitates are made by fragments of other worn down rocks.

a) true

-->  b) false

minerals are created when

a) water condenses to form halite and other salts.

b) water evaporates and mineral components dissolve.

-->  c) water evaporates and minerals precipitate out.

d) none of these.

diagram questions

No diagram questions associated with this lesson