WEBVTT

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(music)

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- Wow.

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Oh hey Fernando.

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Where are we?

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- Hello John.

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This large area here at
Blanchard Springs Cavern

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is called the Grand Canyon.

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Remember the little trickle
of water we saw earlier?

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Well, it's been joined by more
and more trickles of water

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moving through the rock

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to create this large and
beautiful underground river.

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Like we said, caves form
over millions of years.

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Here in Arkansas, caves
form in limestone rock.

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Water moves from the surface, as we saw,

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through cracks and porous
spaces in the rock.

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Surface water starts out slightly acidic

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and can pick up acid
from microbes in the soil

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as it moves down into the subsurface,

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creating caves and larger
pathways for water to flow.

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As you said above ground,

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these areas are known as karsts,

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a word from a beautiful area in Virginia

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where this was first described.

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- As groundwater dissolves limestone,

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it picks up calcite,

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the building block of most
cave formations like these.

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How water moves determines what shape

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these formations take.

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The one thing for sure is that

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they take millions of years to form.

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Here at Blanchard it takes about 150 years

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for one cubic centimeter
of calcite to deposit,

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which is about the size of an almond.

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- 150 years to grow the size of an almond?

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That's going to make
this taste even better.

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What?

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You didn't want one did you?

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- So cave formations like

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stalactites and stalagmites, right?

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- Hey actually I have a good way

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to remember these formations.

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Stalactites are the ones that
hang tight to the ceiling,

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and stalagmites might
grow big and tall one day.

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- That's right Amtchat.

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They give us some clues
about how this cave

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and the world around it might
have looked in the past.

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- As you've learned,

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caves have relatively
stable microclimates that

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make them ideal to record the
local climate of the cave.

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As I mentioned,

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this cave formed from water
coming down from up above,

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but some caves form through water

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moving up from below, or a combination.

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Some caves form completely differently

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in other types of rock.

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Like lava tubes in places like Oregon,

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Washington, or Hawaii.

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Caves can form along
coastlines as sea caves

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through the mechanical erosion
caused by wind and waves.

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Or they even form in glaciers.

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These types of areas
are called pseudo-karsts

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because they don't form
through dissolution

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like caves in limestone,
marble, or dolomite.

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- So why and how exactly do you map caves?

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- I work with the Cave Research Foundation

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and we map caves so we can
understand how they form

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and where the water flows.

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This team here is working
on mapping a cave right now.

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They use a laser, called a
disto, to measure distances.

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- 9.3 meters.

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- And an inclinometer to measure

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vertical extent of the cave.

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So you can hear them
calling out measurements

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and Fernando is the sketcher.

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He is making an actual 3-D
sketch of the cave on paper.