Chemical Weathering Features

Weathering Rind (Chemical)

(Chemical) Outer part of a rock weathers more/faster than the inside

Why - Water/air enters cracks + holes

Rounded Boulders (Chemical)

Via Chemical weathering

How Form? - The points weather first/fastest bc there is more surface area.

Hoodoos (Chemical)

Pillars of rock w/ resistant caprock

Caprock - Resistant Rock at top of pillar

How form? -

1. Starts as layers of rock w/ cracks

2. Water/air seep into cracks + weather the rocks around cracks, leaving pillars

3. The top layer(caprock) is more resistant + layers under it are less resistant to weathering, giving them their funky shapes.

Pictographs (Chemical)

(Chemical) Pictures drawn on rock w/ "paints" made of mixtures of crushed, oxidized minerals

Carbonic Acid Caves (Chemical)

(Chemical) Acidic groundwater flows thru cracks in limestone - weathering/enlarging the crack creating caves

Stalactites (Chemical)

(Chemical) Hang from ceiling (C for Ceiling)

How Form? - Water containing dissolved limestone drips from ceiling of cave. Water cools/evaps causing the limestone to be deposited.

Stalagmites (Chemical)

(Chemical) Protrude from ground (G for Ground)

Water w/ dissolved limestone drips onto floor. Some water evaps/cools causing limestone to be deposited.

Columns (Stalactites + Stalagmite) (Chemical)

(Chemical) Columns form when Stalactites and Stalagmites meet in the middle - forming single column of rock

Gypsum Crystals (Chemical)

(Chemical) Huge gypsum crystals

How Form? - Form in caves - as hydrology changes water - slowly evaps - causes minerals to precipitate out

Sink Holes (Chemical)

(Chemical) Holes in ground formed when roof of a cave collapses

Karst Topography (Chemical)

(Chemical) Unusual rock formation created by weathering of limestone due to infiltration of groundwater containing carbonic acid.

How Form? - Starts as sheet of limestone w/ cracks/joints - water gets in -> dissolves rock around it - as the rock around the crackers weather away - leaves pinnacles(points) of unweathered limestone in pattern of the cracks.

Tanks (Chemical)

(Chemical) Waterholes

How Form? - Water puddles on rock - dissolves cement btwn sand grains - leaves large depression

Solution Holes (Chemical)

(Chemical) Groundwater seeps thru and dissolves cement in the sandstone - leaving holes in the rock

Natural Arch (Chemical)

(Chemical) Water runs down side of rock thru joints - weathers side more than resistant caprock.

How Form? -

1. Starts w/ several joints in rocks that allow water in - increasing rate of weathering along joints.

2. Spaces in btwn joints grow larger (bc weathering) - leaves stands of rock called "fins"

3. Water flows down fins - weathers layers of rock under caprock faster than caprock itself

4. Eventually a hole will form - if caprock doesn't collapse, you have an arch

Alcoves (Chemical)

(Chemical) Form in same manner as arch - but doesn't occur on a fin = so no hole thru other side. (Caprock creates protective cover over the "hole".