Lake Hévíz is the biggest, biologically active
natural medicinal lake in the world with a surface area of 4,4
hectares.Its temperature is the result of the mixture of
the cold and hot spring gushing out from the depth of the
Earth. 410 litres water of 40 degrees Celsius come up every
second from the cave spring, which is 40m below the surface.
Due to this water output the
water of the lake changes completely in three and a half
days. In summer the temperature of the lake is
37-38 degrees Celsius near the surface however it does not decrease
below 24-26 degrees Celsius even in winter. Average water
temperature is 30,7 degrees Celsius.
Therefore it is suitable for bathing all year long. In
Hévíz modern medicinal tourism has a more than 200-year-old
past.
The lake „works” by a special mechanism. The mist
that forms over the lake at night acts as a cushion, preventing the
heat from gushing out with the water, so it provides a uniform
temperature in the lake area.
The
discovery of the spring crate and the
cave
Lake Hévíz had kept its secret for a long time
because of its great depth.
Thef first arrived to explore it in 1908, but they
only reached for 22m because of the extreme
heat. Later, in 1953 they
reached the bottom but couldn't enter the inside of the spring
crater. In 1972 two divers
discovered a narrow gap at the bottom of the lake, 60-80cm high and
2-3m wide, which turned out to be the entrance to the
cave.
Finally, in 1975 István Plózer and his team
entered this narrow gap where they had to fight against 39,5°C heat
and a strong current of 30-40 thousands of liters of water. After
this narrow gap they found a cave of 17m of diameter. There they
found the secret of Hévíz, two springs. On the eastern side they
found a colder spring (26,3°C), and on the western, a hot spring
(41°C). The amount of the hot water is 9 times bigger than the
discharge of the cold spring, so when they mix, the resulting
temperature will be 39,5°C.
The Lake was formed in the Triassic period, along
a tectonic fault line. The cave itself was formed later, in the
Pannonian period, by the currents and the turbulence of the
water. The entrance to the cave can be
found at 38 meters of depth. It is regularly cleaned out by
scientists to regulate the amount of water coming out, and of
course to make possible for tourists to enter it.
The depth of the cave is 40m, the width is 17m and its
altitude is 14m. The cave is popular
among divers.
How was the Lake of Hévíz formed?
The answer lies in the past, in the history of our
Earth looking back to several million years. At the beginning of
the Mesozic era, during the Triassic period (about 200 million
years ago) crystal-clear sea water covered this region as well as
the site of the present day Transdanubian Mountains. Out of this
sea snow-white dolomite and limestone formed a deposit around
Hévíz.
During the other two Mesozic periods, the Jurassic and
the Cretaceous (about 180-170 million years ago) the sea withdrew
from this area. In the territory of the present day Bakony Hills,
at the end of the Cretaceous period and the during the first epoch
of the Tertiary period, the Palaeocene bauxite deposits formed in a
tropical environment, then redeposited due to surface impacts.
These natural forces caused erosion in the softer layers of the
ground surface, at some spots totally destroying them. Then started
the karstification of limestone and dolomite.
During the Tertiary period even the Eocene, the
Oligocene and the Miocene epochs following the Palaeocene did not
leave layers behind, the region of Hévíz remained a 'mainland'. The
last epoch of the period, the Pliocene, however, was very
eventful.
At the end of the Pliocene and at the beginning of the
Pleistocene (about 2 to 4 million years ago) the wind and water
streams carried the majority of the material of the Pannonian
layers southwards. The welling up of hot springs, and thus the
Primordial Spring were the first sign of postvolcanic activities.
Due to earth movements and the crustal collapse two trench systems
were formed in the middle of the Pleistocene epoch. Moisture
accumulated in them: Lake Balaton was formed about 22 thousand
years ago. This was the time when the history of the Lake of Hévíz
also started.
There are several pieces of evidence proving that the
thermal water of the Lake of Hévíz did not well up at the level in
the geological past it does today but much higher. The water of the
Hévíz Lake welled up at its present site about 20-22 thousand years
ago, simultaneously with the formation of Lake Balaton. The warm
water rushing up first flowed into Lake Balaton. Due to the changes
in the climate the water level of Lake Balaton dropped. A peat-moor
formed from the once lush flora in the former basin of the
lake.
The boggy, peaty, flat surface of the Hévíz valley
extends 1-1.5km eastwards of the lake as far as Mt. Dobogó at the
eastern part of the valley and the mountain range of Cserszegtomaj
surrounding the valley from the east. The peaty area extends
southwards as far as river Zala and northwards as well as the
country tavern of Gyöngyös.
The water of the Hévíz Lake is 'heated' by geothermal
energy. The deep-seated waters enclosed in underground storage
systems formed during the Triassic and the Pannonian periods are
heated by heat conducted and radiated from deep-lying layers of the
crust of the earth.
Based on the amount of carbon isotope in the water
scientists have found out that the cold rill of the spring - from
the period of penetration till the date of welling up - is 5-7
thousand years old, while the warm-water spring is 10-12 thousand
years of age. Waters infiltrating into the depth from the surface
come from a quite extensive area: from the Bakony Hills, the
Keszthely Mountains and the Zala Hills. A part of the water does
not permeate too deep into the ground (as far as the Pannonian
layer) - this is the so-called karst water zone - and from here it
gets into the 'mixing cave' of the Lake of Hévíz through the cold
rill. The majority of the water gets much deeper, into the Triassic
dolomite layers where it gets warmed up. During its journey it
dissolves various metals and minerals, then it flows towards the
surface again to arrive finally at the spring cave.
If you want to check
in the Earthcache, you have to perform the conditions (foto
upload to your log):
1. Take a picture of your with the GPS on the bridge on the
given
coordinates. (foto-spoiler)
2. How deep under the water level is the entrance
to the cave?
3. How big is the radioactivity in 1 litre water from the
lake?
Um diesen
Earthcache loggen zu
dürfen:
1. Machen Sie
bitte ein Foto mit GPS auf der Brücke. (foto-spoiler)
2.
Wie tief ist der Eingang der Grotte unter der
Wasseroberfläche?
3. Wie große ist die Wasseradioaktivität in ein liter
Wasser?
Az
Earthcache megtalálásához a következo feltételeket kell
teljesítened. (a loghoz fényképet kell
feltölteni,
a válaszokat a profil oldalamon található Send Message linkre
kattintva e-mailben írd meg!)
1. Készíts egy képet magadról a GPS-el a hídon a megadott
coordinátánál. (foto-spoiler)
2. Milyen mélyen van a forrásbarlang bejárata a vízszint
alatt?
3. Mekkora a rádioaktivitása a tó 1 liter
vizének?
Jestliže si chcete zalogovat tuto
Earthcache, musíte splnit tyto podmínky (foto pridej k tvému
logu):
1. Vyfotografujte se s GPS na mostu na výchozích
souradnicích. (foto-spoiler)
2. Jak hluboko pod hladinou jezera je vstup do
jeskyne?
3. Jak velká je radioaktivita v 1 litru vody z
jezera?
Ako htete zapisati
ovu cache, morate realizovat ove narave:
1. Uradite vaši sliku sa GPS na mostu.
(foto-spoiler)
2. Kako duboko ispod vode je ulaz do jame?
3. Kako velika je radioaktivnost u 1 litru vode iz
jezera?
Thank for translation to the cacher Patikus and I3oris.
