Geo of National Parks Exam 2

Most natural caves are found in

Carbonate Sedimentary rocks (limestones)

Many limestones formed in

Ancient Reefs

Carbonate Rocks are primarily made out of

limestone, sometimes dolomite/dolostone

Carbonate Rocks are from what process

Chemical or Biochemical processes

what are the 3 Abundant rock-forming carbonate minerals

Calcite, aragonite, and dolomite

In carbonate rocks, Calcite can almost be considered 2 distinct minerals:

Low-mg Calcite (<5%) and High-Mg Calcite (5-18%)

Term that means: unstable near the surface

thermodynamically favored

what happens to CaCO_3 Below the lysocline

pressure effects increase solubility

what happens to calcite Below the Carbonate Compensation Depth (CCD)

dissolves more rapidly than it precipitates, and carbonate is not preserved

primary source of carbonate deposition

Sub-tidal, well-illuminated seafloor

when does Cementation begin

very shortly after deposition.

in what conditions are Reefs formed

in shallow waters by biological activity, usually by organisms that secrete CaCO3 skeletons

Modern reefs occupy what percentage of the ocean

<0.1%

Percentage of habitat the Modern reefs provide

25%

Modern reefs are built by what?

Corals

Modern reefs are usually below what ?

breakwater

Modern reefs are formed in what conditions?

warm, shallow water

Continental crust not always above sea level can form what out in the ocean?

Continental Shelf

How do you know a Transition happened in the continental crust

Sharp increase in water depth

Determine each reef

Fringing, Patch, Barrier, Atoll, Bank or platform

3 groups of organisms:

Framebuilders, Binders, Encrusts

what are Framebuilders?

organisms that create the rigid framework (mostly corals in modern times, but also sponges and calcareous algae)

What are Binders?

organisms that bind pre-existing sediment together

What are Encrusters

organisms that do not build large structures, but encrust over surfaces

Two major minerals are composed of calcium carbonate (CaCO3)

Aragonite and Calcite (they are polymorphs)

What are polymorphs ?

minerals with the same chemistry, but different structures.

This is a polymorph with an orthorhombic structure. Is easier to precipitate, but is not thermodynamically stable at low pressures.

Aragonite

This is stable, and aragonite in rocks will eventually turn into this. Most limestones are made of this.

Calcite

dead corals & other skeletons are cemented together into what?

Limestone

what are Reef Crest?

High point of reef, formed by framebuilder organisms.

What are Back Reefs?

Sediment deposited on back (quiet) side of reef in shallow lagoons and are fine-grained, very gentle tilt.

What are Fore Reefs?

Faces deeper water side of reef. Debris may be broken off and flow into deeper water. Home to encrusters.

Biscayne NP is what % of water

95%

What is Florida Keys

A chain of limestone islands, known for their coral reefs.

Florida Keys Climate

Subtropical

How old is the Biscayne Bay

3,000 t0 5,000 years old

Most of the Florida Keys are composed of what?

Key Largo Limestone

What is Key Largo Limestone?

The remains of a coral reef that once stretched over 220 miles along the south coast of Florida

Pleistocene age, most dates cluster (Years of last interglacial)

140,00 to 100,000 years

When is the Pleistocene age?

< 2.58 Million years

Why is the Northen area of Biscayne Bay referred as “Safety Valve”

Contains sand flats that serve to protect the bay from storm surge and flooding.

Year of Dry Tortugas National Monument

1935

Year of Dry Tortugas became a National Park

1992

Why was Dry Tortugas established as a National Park

To protect natural ecosystems (coral reefs, seabird breeding grounds) as well as Fort Jefferson.

Who first visited Dry Tortugas

Juan Ponce de León in June, 1513

What happened to the construction of Fort Jefferson?

It was halted due to the Civil War and was never finished

How many known species of birds in Dry Tortugas?

299

Where is Dry Tortugas NP located

On the southern edge of the “Florida Platform”

What is the Florida Platform

A broad, mostly flat carbonate platform ranging from slightly above sea level to ~90 m/300 ft. below sea level.

What is the Pleistocene age?

Where the Earth's climate kept switching between cold periods (called glacials) and warmer periods (called interglacials)

The Western Florida Keys are composed which places?

Miami and Key Largo Limestones

Place has deeper bedrock

Key Largo Limestone

Place is often has “oolite sands”

Miami Limestone

What is a Oolite?

a limestone of ooids–spheroidal grains of calcium carbonate (usually originally aragonite) with a layered structure

Ooids are usually formed around what?

A nuclei of fossil fragments or clastic material nuclei of fossil fragments or clastic material

Common reef-building corals are what?

brain corals and star corals

what are Spurs and Grooves?

growth patterns of fast-growing corals in areas with high wave energy

What are Reef Rubble?

dead, unstable coral due to disease and/or storm damage

This national park was the first NP created specifically to protect an ecosystem?

Everglades NP

What is the consequences of Everglades NP being a Subtropical wetland?

Bedrock is very little-exposed

What happens to limestone rocks when they’re exposed to water?

Small holes are formed because the water is a little bit acidic and slowly eats away the rock

Two main types of soils in Everglades?

Peat soil and marl soil

What is Peat Soil?

Product of years of decomposing plant matter

What is Marl soil?

grayish, carbonate-rich mud produced by decaying of algae and calcareous microorganisms

Landscape Evolution

1. Rainwater seeps into the ground

2. Cavities form underground

3. The ground collapses

4. Plants start to grow

5. A swamp forest forms

What is Porosity?

empty space in rocks available for water

What is Permeability?

The ability for water to flow through the rock.

Why are the Everglades swamps currently threatened?

bc channelization of water flow and depletion of Biscayne Aquifer

Why is rain more acidic then pure water

bc rain picks up CO2 from atmosphere

Over 90% of caves in limestone are formed due to
dissolution by what

Carbonic Acid

Term for, Void spaces often unstable and collapse

karsting

What are 2 major groups of rocks associated with caves

Evaporite rocks and Carbonate rocks

Which minerals are most commonly found in speleothems

calcite (CaCO₃)

What factors influence the shape and formation of speleothems inside caves?

their location within the cave, the local water chemistry, and air flow conditions.

what is the Rio Grande Rift

Continental rift from southernmost CO through NM into TX and Mexico.

How was the Rio Rift in early Permian time

was tropical and coastal, which allowed formation of large reef complexes

When was Capitan Reef Complex formed and by what?

in early-middle Permian, and built by
sponges and calcareous algae.

What is Breccia?

A rock made of angular, broken rock fragments that have been re-cemented together.

What happen to Salt Basin

caught rainfall in Pleistocene time, had
nowhere to drain, so evaporation left behind large amounts of gypsum

what 2 parks have the same features and are formed with the same rocks

Carlsbad Caverns NP and Guadalupe Mountains NP

What was the Carlsbad Caverns popular?

was mined for guano

The Carlsbad Caverns was formed in the same
Early Permian reef as which places?

Guadalupe Mountains, Apache Mountains, and
Glass Mountain

The Carlsbad caverns is mostly formed by acid

Sulfuric acid

Why are the oldest caves found at higher levels?

They were formed first when the water table was higher

What does it mean when a cave is "below the water table"?

It's in an area full of water underground

What happened after the water table dropped

Caves were revealed and exposed

Where can you find the youngest caves — higher up or deeper down?

Deeper down

What are most speleothems made from?

Groundwater rich in CaCO₃ and CaSO₄

What are Stalactites?

They hang from the roof of a cave

What are Stalagmites?

They grow upward from the cave floor.

Why do Cave popcorn sometimes
form on only one side?

bc of airflow conditions

What is “cave cotton”?

A fibrous form of sulfate speleothems

Which mineral is cave cotton occasionally made from?

Gypsum

In Carlsbad Caverns, cave cotton is often made of which minerals?

Thenardite and mirabilite

Under what conditions is cave cotton most likely to be found?

Cold and dry seasons

What can destroy cave cotton?

Heat from lamps or warm, moist air from breathing

What was Mammoth Cave History

Mined for saltpeter and other nitrates beginning in 1798; major source of nitrates during War of 1812. Then it was turned into a tourist attraction. Then it was used tuberculosis clinic by dr. John.

Who was Stephen Bishop

made the first extensive map of the Mammoth Cave

longest Known Cave system in the world

The Mammoth-Flint Ridge Cave System

What are Joints?

Regular fractures in the rock