Weathering and the formation of sedimentary rocks Prof

Weathering and the formation of sedimentary rocks • All materials are susceptible to weathering

Mechanical Weathering Rocks are brocken into smaller pieces • This type of weathering enhances

Frost Wedging alternate freezing and thawing of water Water increases by 9% upon freezing

Unloading Exfoliation dome and onion-like layers

$Biological Activity Root wedging widens fractures in rocks and helps in mechanical weathering$

Chemical weathering: alters the internal structure of minerals by removal and/or addition of new

ap o Ev rit es ica m he oc Bi ed im ls ts

Salt crust along the shore of the Dead Sea

Chalk layers: fine grained friable limestone = shells of microorganisms

Folded thin beds of evaporites along shore of the Dead Sea

Sedimentary structures Ripple marks Mud cracks

Slides: 30

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Weathering and the formation of sedimentary rocks Prof. Dr. Ziad Salem Abu-Hamatteh Faculty of Engineering Technology Al-Balqa’ Applied University

Weathering and the formation of sedimentary rocks • All materials are susceptible to weathering = interaction between materials and weather! • Synthetic and natural materials (concrete + minerals and rocks, iron rods etc. ) • Minerals and rocks that form at high P and T (below or above Earth’s Surface) are unstable on the Surface of the Earth. • They change until they achieve equilibrium with the new conditions. • Weathering processes are broadly divided into mechanical and chemical weathering.

Place of Formation

Sedimentary rock forming processes

Mechanical Weathering Rocks are brocken into smaller pieces • This type of weathering enhances chemical weathering by increasing the surface area exposed to chemical attack!

Frost Wedging alternate freezing and thawing of water Water increases by 9% upon freezing Effective freezing-thawing cycles are common in mountainous middle lattitudes

Unloading Exfoliation dome and onion-like layers

$Biological Activity Root wedging widens fractures in rocks and helps in mechanical weathering$

Biological Activity Root wedging widens fractures in rocks and helps in mechanical weathering

Chemical weathering: alters the internal structure of minerals by removal and/or addition of new constituents • O 2, H 2 O, CO 2 dissolve in water to form carbonic acid, humic acids form by decay of organic matter 2 KAl. Si 3 O 8+9 H 2 O +2 H+ Al 2 Si 2 O 5(OH)4 +4 H 4 Si. O 4 +2 K+

Clastic

Gravel & Sand

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Conglomerate

Breccia

Sandstone

Shale with plant remains

Coquina: shell fragments

Calcareous shells of foraminifera

Salt crust along the shore of the Dead Sea

Diatoms (siliceous shells)

Chalk layers: fine grained friable limestone = shells of microorganisms

Salt flat

Stages of Coal formation

Stratification=bedding=layering

Folded thin beds of evaporites along shore of the Dead Sea

Cross beds in sandstones

Sedimentary structures Ripple marks Mud cracks