Steigerberg: surf cliff of the Oligocene sea
285 million years ago at the geological turning point to the
Rotliegende,
there were strong movements of the earth's crust in the Nahe area with wavelike
shocks and the creation of faults. In the process magma, the molten material
inside the earth, rose towards the surface but without actually reaching it.
The large intrusion blocks created by this movement, which were later exposed
by erosion, are made up of red rhyolite (earlier: porphyry) —like the Rotenfels
and the Rheingrafenstein— or of the somewhat darker dacite, as found on the
Lemberg mountain. Later on, the more liquid magma reached the surface and
covered much of the Nahe area. The lava soon stopped flowing and was, over
a period of 240 million years (periods
Triassic, Jurassic, Cretaceous),
exposed to a mostly tropical climate, where the volcanic rock was
profoundly eroded creating deep valleys. However, isolated blocks of very
hard rhyolite have remained.
35 million years ago, in the
Oligocene
era, there was a down-faulting which created the trench of the upper Rhine.
The region was flooded by a subtropical sea. This sea connected to the open
seas to the north and south of the middle European area. The coastline ran
along the southern edge of the Devonian layers of the Hunsrück with shallow
bays near Bad Sobernheim and Bad Kreuznach. South of Bad Kreuznach, an island
archipelago made up of the remaining rhyolite, massifs were created, consisting
of peninsulas (Lemberg, Vorholz), islands (Rheingrafenstein, Eichelberg, Steigerberg)
and the bays between them (Feilbingert, Weinsheim).
Storms, hurricanes and the corresponding heavy surf activity worked upon the
solid rock of the island coasts, smoothing it. At the time of the Oligocene
Sea's highest level, the smaller islands such as Steigerberg were probably
mostly under water. This is confirmed by rich fossil finds of oysters, clams
and snails. The cliff at Steigerberg and the steep wall behind it shown here
(picture by Kurt-Werner Augenstein) are a geotope, unique in Europe.
Presently there are efforts being made to make this area available to the
public as a site for a geological nature path.