North Tower - Schloss Drachenburg

Sea of Rocks
Geologically speaking, the Schloss Drachenburg forest park
is remarkable for its stone formations – a sea of rocks that
came into being about 26 million years ago during the
Tertiary Period. As the result of volcanic eruptions at the
Drachenfels, enormous quantities of ash were discharged.
The ensuing viscous magma pressed from below against
the layer of ash solidifi ed as tuff – but without being able to
break through. A cryptodome thus swelled up. Next to this
main crypto-dome, to the north west, a rock mass pressed
into the tuff. The body of lava solidifi ed into stone known
as trachyte. Cracks then formed into which surface water
was able to penetrate. Subsequently, as the result of frost
shattering, various blocks broke free of the rock. Along with
the tuff layer, these large trachyte blocks moved down the
mountainside in two fl ows, one of which runs through today‘s
park at Schloss Drachenburg.
Trachyte
The volcanic rock trachyte was fi rst identifi ed at the start of
the 19th century by the French geologist Alexandre Brongniart
(1770-1847) studying rock formations in the Auvergne. The
name comes from the Greek word trachyt which means “raw”,
this due to the fact that the cavities in the stone lend any new
fracture a raw jagged exterior.
Typical for trachyte are the grey colouring and the sanidines
encased in the stone – i.e. the fl at-shaped crystals.
The trachyte found at the Drachenfels was excavated as long
ago as Roman times. Quarries, identifi able by tooling marks
visible on the stones, were located in the western area of the
summit and in the Sea of Rocks here at Schloss Drachenburg.
Drachenfels cryptodome and
Drachenburg rock mass with
tuff substratum
Trachyte stone with tooling
marks from quarry work in
Roman times, found in the
Schloss Drachenburg forest
park.
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