If you would like to pursue a doctorate in one of the geosciences at the University of Cologne, the first step is to find an official principal supervisor. This has to be a person who is legally entitled to supervise a doctoral research project in the Faculty of Mathematics and Natural Sciences (MNF) (a professor or Privatdozent).
Subsequently, you will need to register in Docfile (the online registration system for doctoral candidates) and hand in your Application for Admission as a doctoral student at the Doctoral Office of the Faculty. For this, you will need the (electronic) signatures of your supervisor and the GSGS manager. From this moment you are a GSGS member. For details of the entire PhD procedure and for downloading the latest version of the form visit the Internet pages of the Doctoral Office. For any correspondence with the Doctoral Office, use the e-mail address firstname.lastname@example.org and mention "Geosciences" or "GSGS" in the subject line, so that your message can be assigned to the person in charge of our subject area, Ms Gotzmann.
Please visit the website of the Albertus Magnus Center (AMC - the university-wide center for supporting early-career researchers) for general information on pursuing a doctorate at the University of Cologne, e.g. on how to go about finding a supervisor.