Chapter 13 - Karsts and Caves Flashcards
Define Karst (review)
Karst
is a terrain with distinctive characteristics of
relief and drainage, including caves, sinkholes, underground streams, caverns, arising primarily
from the solution of soluble bedrock by natural waters
Define Soil (review)
Soil
is a naturally occurring, unconsolidated or
loose material on the surface of the earth, capable
of supporting life. Soil has three components: solid,
liquid, and gas
.
Define Regolith (review)
is the layer of
loose, heterogeneous material covering solid rock. It
includes dust, soil, broken rock
(blanket rock)
Define Weathering (also mechanical and chemical) [review]
Weathering
-Weathering is the mechanical breakdown and chemical
a
lteration of rock and sediment when exposed to air,
moisture, and organic matter.
Weathering is “mechanical (physical)” or “chemical”.
Mechanical (physical) weathering
-mechanical disintegration of rocks
Chemical weathering
-decomposition of rocks and sediments via chemical (and microbial) reactions that dissolve minerals
Main products of (chemical?) weathering
Silicates: Regolith and soil
Carbonates: Kart + Caves
Earliest life forms that lived in caves? What do caves tell us about them (evidence) ?
Neanderthals
-cave paintings, 30k to 40k years ago
Define cave
natural opening in rock large enough for man to fit through
Stages of cave formations:
2 stages:
1) Cave formation via DISSOLUTION below groundwater table
2) formation (DECORATION) forming above groundwater level
Stage 1 of cave formation) Dissolution wrt caves
Caves form as a result of the dissolution of carbonate rocks by slightly acidic water
Dissolution; through groundwater
Note; slightly acidic groundwater
- groundwater dissolves carbonate rocks and gradually forms a system of passageways
- groundwater then moves along surface of water table, forming system of horizontal passageways
- as surface streams erode deeper valleys, water table drops, and abandoned channelways form and interconnecting system of caves and rocks
Stage 2 of cave formation) Decoration wrt caves; what are features, how are they made?
-drop of water evaporates in cave
-water drops in from top, first thing that forms is a ring of calcium carbonate that grows downwards
-eventually grows to considerably long length, grows longer and longer
-essentially reading the equation CO2 + H2O –> H2CO3, but backwards
Stalagmites are from bottom up
Stalactite are from top - bottom
How do hybrid caves form? What are features of them?
When sea levels rise due to high tides, cut open an older cave that was higher up
This washes out those cavees, creates a hybrid cave
-they have odd columns, they are weak, doesn’t take much to break
How are sea caves made? Max length?
Corrasion - mechanical erosion of earths surface caused when materials are transported across it by running water, waves, glaciers, wind (think pseudo karst)
-300m max length
Caves made from mechanical weathering
Caves made from chemical weathering
Mechanical weathering:
sea caves
Chemical weathering:
caves made from dissolution(Carbonate with HCL)
define karst
Area of irregular limestone where dissolution produced fissures, sinkholes, underground streams, and caverns
What are sinkholes? How are they formed?
sub circular depressions. USUALLY Formed by dissolution of carbonate rocks (exception: Pseudo sinkholes)
What are pseudo sinkholes
Sinkholes that are not formed from dissolution of carbonate rocks
What are collapse sinks? How are they related to tower karst?
When sink holes sink down into cave system, widen channels for rain water to go down into groundwater, wider and wider opening
- all that is left is a column/tower of carbonate rocks
- the tower of corbonate rocks is a Tower Karst
What are solution valleys?
When sinkholes connect through dissolution and they merge together
-will get flooded during heavy rainfall
What are sinking streams?
Streams that just disappear from surface and go into ground
Karstification - epigene vs hypogene cave systems
Epigene:
Rain water comes down, goes through rock, dissolving through passage way, have an epigene cave system, the water eventually goes underground and goes out to ocean
-on surface of earth
Hypogene:
water that dissolves cave systems come from BOTTOM UP, tends to be mazes instead of like stream caves where they just go down cave
-multiple layers of caves
-under surface of earth
What is epigene?
processes that are controlled from top down
-on surface of earth
What is hypogene?
Processes that are controlled from bottom up
-under surface of earth
Sinkholes in Barbados?
gullies - landform created by running water, eroding into soil
-resemble large ditches or small valleys
2830 sinkholes in Barbados!!
diameter: 9m to 120m
How are stalagmites useful? What can they help identify? Talk about climate of fresh water caves
remember stalagmites are floor up
- they have growth rings like trees
- we can use as an estimation of paleo-climate
- allows us to tell how cold or how wet it was in past climates
For fresh water caves:
-caves are always same temperature year round
Define pseudo karst
karst that is not formed by dissolution of carbonate / limestone
Biggest cave in the world??
Vietnam: Hang Son Dooong (mountain river cave)
-4km x 100m wide up to 300m high
Deepest cave in the world??
Georgia: Krubera cave
2197m
What is bioerosion
removal of calcium carbonate by biological agents (instead of dissolution)
- so its organisms living on rocks, that want to eat algae, so they eat through the rock to get through algae
- generate tiny holes, sea caves, create micro karsts
