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How Do Caves Form?

hidden deep within the Vietnamese jungle

province of kyeong bin lies a secret

wonder of the world that is until 1991

when a local logger named Ho Khan made a

spectacular discovery while searching

for agarwood alone in the forest he

became lost but soon stumbled upon a

massive rift in the limestone

mountainside out from the opening came

billowing clouds the roar of rushing

water could be heard and a strong

constant gust of wind blew out from

between the rocks for fear of the

unknown ho Kahn explored no deeper than

the entrance to this cave 15 years go by

until in 2006 o Khan speaks with two

members of the British Cave Research

Association Howard and Deb Limbert who

travelled to Vietnam to discover new

caves intrigued by ho Kahn's description

they seek him out and urge him to lead

them to it but after many failed

attempts Ho Khan could not rediscover

what he had found by mistake all those

years ago

it's not until 2009 that by pure chance

Oh Kahn finds himself back at the

entrance of this cave wall on another

hunt for wood this time he means sure to

remember its exact location and

contacted the Limbert immediately they

returned to Vietnam as fast as possible

and together with Ho Kahn and a team of

other explorers they take man's first

steps into the massive cavern in the

mountains its uncovered that the cave

runs nine kilometers deep into the earth

with some parts reaching 200 meters high

and 150 meters wide large enough to fly

a Boeing 747 inside these dimensions

make ho Kahn's discovery the largest

cave on earth by volume coming in at

over twice the size of the next two

largest cave in total there's around

thirty eight point five million cubic

meters of empty space within this cave

that's nearly the same amount of space

as the Grand Canyon all hollowed out

beneath the animate Mountains but this

isn't the Grand Canyon this is hyung

song Dule translating very roughly into

English the name comes out as cave of

the Mountain River this name comes from

the fact that a stream of water pours

out from the entrance of the cave a

river seemingly coming from within the

mountain itself miles deep into the cave

jungles can be found inside it's to

build lines which are basically breaks

in the roof of the cave caused by

sinkholes allowing sunlight to shine

deep inside the earth exploring deeper

inside this cave you can find

stalagmites that measure up to 80

meters tall some of the tallest ever

discovered even deeper and you can

discover large cave pearls some the size

of baseballs an occurrence so rare that

you probably didn't even know cave

pearls were a thing knowing all this I

think it's safe to say hyung Seung Jun

is not only a spectacular cave but also

one of the most impressive sights on the

planet but how exactly do caves like

this form in the first place well to

understand this process we actually need

to start in the ocean you see sea

creatures like crabs and corals as well

as tons of microscopic organisms use the

minerals dissolved in the ocean water to

build their shells when they died their

shells are left empty and fall to the

ocean floor once this happens a few

trillion more times the shells will

begin to build up into a layer over time

this layer of shells gets buried and

buried and buried until it's under so

much pressure that it becomes a single

solid rock we call this rock limestone

you've probably heard about it before

and you've definitely seen it it's a

grayish white rock found in many cliffs

and mountains then depending on plate

tectonics this limestone might get

pushed above the sea and that's how we

get limestone on dry land and in

mountains if you're curious this is what

limestone looks like under a microscope

you can still see some of the skeletons

of long dead sea creatures cool right

okay so next we need to know what

limestone is just a few seconds ago I

explained that sea creatures take

minerals from the oceans to build their

shells and the primary material they do

this with is called calcium carbonate

this is a really good building material

because it's strong and it's readily

available in the ocean and can dissolve

easily in ocean water so the materials

get recycled and used by new organisms

that's important remember that limestone

dissolves easily even in weak acids

lastly we need to know how the rain

interacts with the atmosphere and the

soil trust me this will all make sense

in just a second so we all know how rain

is made but for anyone who missed that

day in school water from the ocean

evaporates and maybe some water from

trees of a bow transfer rates then this

water collects and floats into areas of

low pressures and low temperatures and

condenses to become clouds

if this moist air becomes too saturated

with water some of it will precipitate

out and fall to the earth that's what

rain is but before that happens while

still in the clouds the water molecules

interact with the gases in the

atmosphere some of the water will come

in contact with carbon

oxide and sometimes when they crash

together they create carbonic acid a

weak acid but still an asset then when

this slightly acidic rain falls to the

earth and travels through the soil it

can pick up even more acids on the way

down

eventually this acidic water sinks to

the water table and becomes part of the

groundwater

if this happens where there's a layer of

limestone in the soil a slightly acidic

groundwater can eat away and dissolve it

until a cavity in the earth is created

because again limestone dissolves easily

even in weak acids this process can

actually be remarkably fast in geologic

terms hongseong doomed for example is

only roughly three million years old

that's younger than the famous

Australopithecus fossil and human

ancestor Lucy which is 3.2 million years

old then Fisher's imperfections and

sinkholes can create entrances to these

hollow tubes beneath the ground and when

they do you have a cave

if the limestone is on the surface it

can instead be carved into cliffs and

other strange and unique shapes this

type of landscape is called karst

topography and the more rainfall and

area gets the more karst topography can

form and the greater number of caves and

sinkholes there will likely be that's

why Howard and Deb Lambert were in rainy

vietnam looking for caves in the first

place and that's also why it's no

surprise that hongseong doom is where it

is one of the wettest regions in the

world now here's a rough map of where

karst topography is to be found on earth

you can see one of the biggest regions

of karst topography is here in

southeastern Asia right where Han Zhang

Jun is to be found in this area you'll

also find other strange karst formations

like these famous mountains in China

then over here in the United States is

perhaps the second biggest patch of

karst features and it's in this area

that you'll find more famous caves like

Mammoth Cave and Kentucky which is the

longest cave on earth at over 650

kilometres long but let's go back to how

caves form depending on the size and

shape of the limestone layer a few

different types of caves can be created

but almost always a cave will have an

entrance point where water can seep and

called

wallet and to point where the water

empties out a spring in the case of Hong

Hong doom the spring is actually what

we'd consider as the entrance and thus

wallets would be the two holes in the

cave ceiling caused by sinkholes and

that's essentially it there are two

things I should know before ending

however first while limestone is the

most common Rock type for capes to

Foreman any rock that dissolves in weak

acids will form caves over time so

deposits of rocks like dolomite gypsum

and even marble can become caves given

enough time but limestone is by far the

most common second this is how solution

caves are made and there are actually a

few more types of cave in each one forms

in a different way but solution caves

are the most regularly occurring cave

type so I figured that would be the

focus of this video if you want to see

another video on how any of the more

rare cave types form maybe give this

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next week with another video thanks

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