Istidens
slutning
Istidens sidste årtusinder kaldes Senglacialtiden.
Isen var smeltet bort fra Danmark, men mange steder lå der endnu
dødis tilbage.
Landskabet var bart, klimaet vekslede mellem kolde og lune
perioder.
De kolde perioder kaldes Dryas-tider efter planten Dryas
(Rypelyng).
Den tundravegetationsom opstod var ikke i stand til helt at
beskytte jorden mod erosion.
Der opstod blandt andet erosionskløfter.
Et eksempel på sådan en erosionskløft i Horsens-området er Tolstrup
ådal, som løber gennem Hansted Skov.
Sundet mellem Nørrestrand og Horsens fjord er muligvis også en
senglacial erosionsdal, som senere druknede i
havet.
Efter istiden
Tiden efter istiden kaldes postglacialtiden.
Den begyndte for 10.000 år siden.
Første fase afPostglacialtiden var Fastlandstiden, hvor Danmark var
meget større end i dag.
Derefter fulgte Stenalderhavet, hvor en pludselig havstigning
bragte store dele af Danmark under havdækning (se
lokalitetsbeskrivelsen Horsens Fjord).
Siden bragte den isostatisk landhævning tidligere havdækkede
områder over havniveau.
Den isostatiske landhævning er en langsom hævning, som sker på
grund af at jorden befries for isens tryk.
Samtidig med disse niveauforandringer foregik der en
vegetationsudvikling, hvor den ene naturtype afløste den
anden.
Først indvandrede en lys pionerskov.
Den blev afløst af en mørk og tæt skov, som gradvist, via
menneskelige indgreb, blev afløstaf den kultursteppevi kender i
dag.
Hansted
ådal
Under fjorden løber en dal, som ved Horsens drejer mod nordvest og
følger Hansted ådal.
Denne dal menes at være dannet allerede i tertiærtiden ved
jordskorpebevægelser, som fik undergrunden til at revne og synke
ind langs brudlinierne.
Indsynkningen foregår stadig, men meget langsomt.
Istidens gletschere eroderede videre på dalen og udnyttede den også
til transport af smeltevand.
Sidste istids Ungbaltiske is gled ind gennem Horsens fjord, hvor
den delte sig i to istunger.
Den ene tunge fulgte Hansted ådal frem til israndslinien.
Den bakkerække, der afgrænser Hansted ådal mod Gudenådalen er en
randmoræne, skubbet op og foldet af den Ungbaltiske
is.
Opgaven her er:
A: Svar på følgende
spørgsmål:
1: På stedet, er der en sten,
hvilken slags sten er det??
2: På stedet, hvordan kan du
se at landskabet er skabt af istiden??
3: På stedet, bestem med din
GPS hvad højde forskellen er på WP 1 og WP 2
B: Send dine svar til
f.kaihoj@gmail.com
C: Du må gerne tage et billed
og uploade sammen med din log.
Du behøver ikke at vente på svar for at logge cachen, du bliver
kontaktet hvis dine svar ikke er rigtige.
Ice Age
end
Glacial last
millennia called Senglacialtiden.
The ice had melted away from Denmark, but many places were still
dead ice left.
The landscape was bare, the climate alternated between cold and
warm periods.
The cold periods called Dryas times after the plant Dryas
(Rypelyng).
The tundravegetationsom occurred was unable to completely protect
the soil against erosion.
There arose among other gullies.
An example of such an erosion gap in Horsens area is Tolstrup river
valley that runs through Hansted Forest.
Strait between North Beach and Horsens fjord may also be a Late
Glacial erosionsdal, who later drowned in the
sea.
After the Ice Age
The period after the Ice Age is called postglacialtiden.
It began 10,000 years ago.
The first phase was afPostglacialtiden Mainland time when Denmark
was much larger than today.
Then followed the Stone Age Sea, where a sudden rise in sea level
brought large parts of Denmark during ocean coverage.
Since bringing the isostatic uplift previously ocean coverage areas
above sea level.
The isostatic uplift is a slow uplift, which happens because of the
earth freed from the ice pressure.
Along with these changes of level, there were a vegetation
succession, where one habitat replaces another.
Only a light immigrant pioneer forest.
It was replaced by a dark and dense forest, which gradually,
through human intervention, was replaced by the steppe culture we
know today.
Hansted valley
During the fjord runs a valley near Horsens is to the northwest and
follow Hansted valley.
This valley is believed to be formed already in the Tertiary period
in earth crust movements, which had ground to crack and sink in
along the fracture lines.
Subsidence is still going on, but very slowly.
Ice Age glaciers eroded further in the valley and used it also for
the transport of meltwater.
Last glacial ice Ungbaltiske slid through Horsens fjord, where it
broke in two istunger.
One tongue followed Hansted valley up to the ice front.
The hill range, bounding Hansted valley against Gudenå valley is a
lateral moraine formed, pushed up and folded the Ungbaltiske
ice.
The task here is:
A: Answer the following
questions:
1: On site, there is a stone,
what kind of stone is it?
2: On the spot, how can you
see that the landscape has been created by Ice Age?
3: On the spot, fix with your GPS altitude
difference is between WP 1 and WP 2
B: Send your answers to
f.kaihoj @ gmail.com
C: You can take a picture and
upload along with your log.
You do not have to wait for answers to log the cache, you will be
contacted if your answer is correct.