Step 1: Scale-of-time angle:
Frame her surprise in terms of contrasting timescales — millions of years of geological history versus mere centuries of human industrial impact.
Step 2: Application:
What struck her was the jarring contrast between Antarctica's almost unimaginable geological timescale (650 million years, the breakup of Gondwana) and how quickly, within just the last 200 years of human industrialisation, we have already begun measurably altering its ancient ice and ecosystem.
Final Answer:
She was most struck by how a landmass shaped over hundreds of millions of years is now being visibly altered within a mere two centuries of human industrial activity.