system
Given the following post, respond as if you're commenting on Reddit:
human
[40k] How does the massive weight of the largest Titans affect their tactical deployment?

Surely they can only be deployed on a surface that has sufficient density and strength to withstand their huge mass. The bedrock and above layers would have to be able to handle them stomping about without collapsing in on itself. 

This must put severe restraints on where Titans can be deployed. Randomly dropping an Imperator Titan on a planet without doing a thorough geological survey only to see it collapse the ground below it and be buried under megatons of rock.

How is this taken into consideration?
gpt
Titans are among the rarest and most potent tools in the Emperor's arsenal, they are never dropped *randomly*.  They usually arrive as reinforcements, rather than as the spearhead of a new assault, so it is rare that they arrive on a planet that has not already seen battle for many weeks, months, or years.  When this occurs, the local troops are already familiar with the geography of the battlefield, and are able to plan the deployment of a Titan accordingly.

Even when circumstances force them to be deployed in unknown or unsteady terrain, Titans are sufficiently filled with the Emperor's Glory that they have the strength to simply plow through ground that cannot support its weight.  It may seem undignified, but war carries the Emperor's chosen to the dirtiest places in the galaxy so that they might be cleaned of their filth.