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This cache takes you inside a landscape shaped by the last ice
ages known as the Mecklenburgische-Brandenburgische Seenplate and
specifically to the Roofensee.
The term "ice age" denotes a geological period in
earths history with long term reduced temperatures resulting in the
formation and expansion of ice shields at at least one pole. In the
scientific community this geological period is more precisely
called a galcial age.. The latest glacial age, the
Pliocene-Quaternary glaciation is thus still ongoing, since the ice
shield in the arctic (north pole) and antarctic (south pole) are
still present.
Within a long-term glacial age there are several glacial
periods or alternatively "glacials" or
"glaciations", when temperatures drop and ice shield
expand, or intermittent warm periods are called
"interglacials". The term "ice age" in
colloquial language often refers to the last glacials in this
period. The term will be used with this meaning in this text.
In northern Europe and the lowlands of northern Germany, that
comprise the Mecklenburgisch-Brandenburgische Seenplatte,
especially the last ice ages, named here after local
rivers, were formative for the landscape of today. Moraines next to
the former edges of the ice shields and glaciers, glacial valleys
formed by the melting water and glacial erratics are typical for
this area.
The formation of the landscape is not a terminated, but an ongoing
process. Currently the forces of erosion, the
weathering of structures by wind and water, and
silting, the deposition of silt in dips and lakes are
the main drivers of landscape formation.
The bogs or moores as areas where silting becomes
visible are of specific interest, since they are not just forming
the landscape, but also the first stadium of a geological process
that transformes dead organic material first to
peat, afterwards to lignite, then
steam coal and finally anthracite and
graphite.
The Roofensee is a typical example of a kettle
lake without natural rivers or creeks as water source or
drain. Due to the specific geological properties of the terrain
several types of bogs or mores can be seen along this
trail.
The bogs are accessible by the Moorerlebnispfad,
a route established by the Landesumweltamt
of Brandenburg. Most information in the following text is also
from them,
Stage1: Aufbruch - Raised Bog
The Grubitzwisch belongs to the developmental type called raised
bog. These develop from a lake or flat marshy area, over either
non-acidic or acidic substrates. Over centuries there is a
progression from open lake, to marsh, then fen (or on acidic
substrates, valley bog) and carr, as silt or peat fill the lake.
Eventually peat builds up to a level where the land surface is too
flat for ground or surface water to reach the center of the
wetland. This part therefore becomes wholly rain-fed
(ombrotrophic), and the resulting acidic conditions allow the
development of bog (even if the substrate is non-acidic). The bog
continues to form peat, and over time a shallow dome of bog peat
develops: a raised bog. The dome is typically a few meters high in
the center, and is often surrounded by strips of fen or other
wetland vegetation at the edges or along streamsides, where ground
water can percolate into the wetland. This specific bog started
from a side basin of the Roofensee. Once the water is completely
overgrown the growth of the bog will usually stopp. The
Grubitzwisch however is located in a dip, so that water flows in
from the hillsides.
Stage 2: Vielfalt - marsh area
The Schleusenwiese is spart of the outer zone were the lakes
develops into wetland. This lake is clear water and rich in lime.
The transition of lake into wetland started here with the
deposition of lime silt. The next layers of peat were formed mainly
of reed, but also of sedges. Starting at a depth of 3,25 m major
layers of silt exists, who couldn’t be perforated by drilling
with manual power. The assumption is obvious, that the development
began after the last ice-age. The lake fills from its western end
with silt and peat, a process still continuing today.
Stage 3: Kessel Saures – Basin Bog
The „Moorkessel an Dietrichs Teerofen“ is a basin bog.
These bogs grow on top of other bogs and are therefore called
secondary development type. In this specific case the valley bog
grows on top of a classic raised bog. The history of this site is
an enigma due to the shallow depth and the first silt layer which
consists of peat clay here. Such silts form when soil paricles
(i.e. clay) are entering the basin. They seal the basin and help
the water to stay in the dip. Thus a small lake is formed which
starts to silt up immediately. Therefore it is called a raised bog
initially. One question is how the clay gets into the dip. Soil
particles move only in such areas, where no closed coverage with
vegetation retaining such soil, exists. If a stronger impact of
water or wind happens here, particles are dissolved and moved
along. In a dip like this one they accumulate and deposit finally.
Currently one can not identify such a non closed vegetation
coverage. But one must remember that the formation of such bogs
takes a significant amount of time, so the silt layer made of clay
was deposited long ago.
Stage 4: Großer Barschsee – Basin Bog
The „Große Barschsee“ is a real basin bog that grew on
top of a raised bog, but its silting up started right after the end
of the last ice age. The melting of a large ice blog initially lead
to a kettle lake, which immediately began to deposit silt and
develop into a marsh. Layers of silt found in the deeper areas of
the bog indicate this development. Due to variances in the climate
after the last ice age different amounts of peat were deposited
each year. During very dry seasons the growth of the bog stopped
almost completely. The upper layers of the soil are no longer
saturated with water and trees like birch or pine can grow. Larger
bodies of water (like this one once used to be) take longer to
develop into marsh and bogs and sometimes contain a relic body of
water in their center. This remaining body of water, called
"Moorkolk", can be seen here. 2.000 to 4.000 years ago the
formation of peat started again. The return of peat formation
became possible due to rainfall. The water accumulated in the dip
due to the relief structure of the small drainage area of this
bog.
Stage 5: Bruch am Roofensee - Erlenbruch
The „Erlenbruch“shows the direct siltation zone of the
Roofensee. When the lake was formed after the last ice age this
part was all open waters. Since then the deposition of silt has
continued, and the layers are more than 3m thick today. These silts
are of the peat clay type according to the type of water they
originate from. On top of these silts early peats starts to grow as
a result of the main pioneer plant: reed. Later also sedge
contributed to further peat building. Opposite to the silt layers
the peat layers are much less thick. Such areas are characterized
typically by fluctuation of the water level throughout the year.
They are flooded in spring and may fall mostly dry during summer
time. The construction of the Pelzowkanal that you can see here
regulates these naturally occurring water changes. Excess water was
partially drained of by this canal.
Conditions for
loging:
Answer all questions and send an email to the following
address:
(Question1)_(Question2)_(Question3)_(Question4)_(Question5)_(Question6)_(Question7)@cicero14513.de
Without the brackets of course, but please write your geocaching
nik in the subject line. You should receive log approval right away
(check your spam folder though).Please upload a picture of you and
your GPS at the given position (optional).
Question1:
The latest three glacials in northern Germany are named after
rivers. The answer to question one is the first letter of each of
the three rivers with the one for the oldest ice age at the first
position (i.e. rew for Rhine Elbe Weser)
Question2:
At the trailhead you will find several information boards that will
help you to get familiar with the area. One board has the title
"Von Moor zu Moor". In the upper left corner there is a text block
ending with a number. This number is the answer to question2.
Question3:
The age of this bog can be determined quite exactly because of
another, completely different geologic event. What type of event?
The answer to question3 is=(number of letters)-2
Question4:
At stage 2 several boards are explaining the stages of the
formation of this type of bog. How many boards/stages are described
(boards are numbered at their right site).
Question5:
How many stages (without "und so weiter...") are shown on the
wheel?
Please take a photo of yourself with your GPS in front of the
information wheel and upload with your log (optional).
Question6:
The age of this bog can be determined because of the same geologic
event mentioned in question3. What is the age of this bog and how
deep is it? Calculate the average growth in 500 years - the number
in cm (only the number before the decimal point) is the answer to
question6.
Question7:
This stage emphasizes on a specific plant. The answer to question 7
is first letters of the two words comprising the complete latin
anme. i.e. qr for Quercus robur.
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