Well, A timeline...
Quaz 43.23.5 (approx) - A series of geolocial events "Earthquakes"* struck Northern continent. One Quake results in a crust drop of 400 sia. Resulting water, wind and ground displacement from this event destroyed human civilization. Follow-up events, including "volcanic eruptions"* effectively steriled Planet.
Quaz 65.13.11 - Survey mission arrives to investigate sudden ceasation of signals from "Earth" 250 Quaz earlier. Survey teams find signs of once planet-wide civilization that was eliminated be geologic event (NOTE: No sign of orbital collision found during mission.) Teams finds, at widely scattered locations near what seem to have been largest settlements, examles of written and recorded documentation regarding geologic events. Most material damaged, primarily by corrosive elements in immediate post event atmosphere.
Teams found no senient life forms. Largest surviving land creature is six legged exoskeleton approx. .05 sia in length. (NOTE: Samples of all representative types of surviving animal and plant types gathered for further analysis.)
Recommend that permanent orbit science station be placed in planet's orbit. Geologic event that snuffed out "Humans"* is unprecedented in our records and violates all known geological and planetary standards as known throughout the Arm. DO NOT recommend leaving Survey Teams on planet surface due to utter unpredictability of events.
Gtki ZA GrGa
Survey Mission Science Officer in Charge
* Native words from one of Planet's main languages.