In my experience, 24mm is essential for those huge Iceland views. Over the years Ive tried many setups and 28mm usually leaves me wanting more for landscapes.

• Sony FE 24-105mm f/4 G OSS: Best range for travel and great sealing, but you lose the f2.8 aperture.
• Sigma 24-70mm f/2.8 DG DN II Art: Great alternative thats lighter and cheaper than the GM. Honestly, the 24-105mm is the ultimate one-lens solution for Iceland.

Building on the earlier suggestion, you definitely want to prioritize reliability for a trip like this. Iceland is brutal on gear and you really dont want to be swapping lenses in a storm. If you want to play it safe, I would suggest looking at these:

• Sony FE 24-105mm f/4 G OSS: Honestly the most conservative choice. Its got great weather sealing and that 105mm reach is a lifesaver for distant cliffs. Since you only want one lens, this covers everything safely.
• Sigma 24-70mm f/2.8 DG DN II Art: If you really need f/2.8, this is a more rugged alternative to the Tamron. Just be careful with that 28mm limit. In my experience, standing on a windy beach trying to fit a glacier in the frame is when you really regret not having 24mm. Better to be safe than sorry with your only lens... especially since you are leaving so soon.

To add to the point above: I actually disagree on 24mm being the limit. The Sony FE 20-70mm f/4 G is technically superior for wide vistas and its very light.

Just saw this and honestly, the struggle of finding that perfect one lens for a high-stakes trip like Iceland is actually the worst! I spend hours looking at MTF charts and weather sealing diagrams and it still doesnt feel like enough. When you look at the gasket designs and how moisture ingress works on these zooms, its terrifying. The Sony FE 24-70mm f/2.8 GM II has amazing sealing with rubber rings at every join, but it still extends. Every time that barrel moves, you are basically acting like a bellows, sucking in that Icelandic mist and fine volcanic dust right into the internal cam system. It drives me crazy! I get so frustrated because you want that f/2.8 for the low light, but then you are terrified of the mechanics failing in a storm. Even the Tamron 28-75mm f/2.8 Di III VXD G2 is fantastic for the price, but that 4mm difference isnt just about field of view... its about the whole optical formula and how many elements are moving inside. Trying to balance linear motor torque, weight, and environmental sealing without spending a fortune is basically impossible and it makes me so stressed out just thinking about it!