Complex sentence: Roughly charted in 1898 by the German expedition under Karl Chun, it was re-charted and named in December 1927 by a Norwegian expedition under Captain Harald Horntvedt.
Split into simpler sentences: Roughly charted in 1898 by the German expedition under Karl Chun. Recharted and named in December 1927 by a Norwegian expedition under Captain Harald Horntvedt.