Brass knuckles are often incorrectly portrayed as the weapons of...
Have you ever tried to anchor a tent peg, fence post, or other stationary object in the ground, only to have that ground give way? It's frustrating to say the least, especially when you're dealing with extremely soft surfaces like fresh snow or fine sand. It doesn't matter whether you're trying to stop an EZ-Up tent from blowing over at the beach or rappel down an alpine cliff — strong in-ground anchor points are essential.
Obviously, pounding an ordinary straight stake into the soft sand or snow isn't going to work, since it'll pull straight out again. There are specialty stakes made for use in sand, but if you don't own any, you'll need to improvise anchor points. Fortunately, this isn't a new problem, so solutions already exist.
One time-tested method for anchoring a line to soft soil is called the T-slot anchor. As you might guess from the name, this method involves digging a T-shaped trench into the ground, and tying your line to a straight object placed in that trench. The straight object can be a pair of skis, an ax, a walking stick, or even a rifle. This distributes the line's tension across a wider area, so your anchor won't pull out or slip.
The second part of the “T” formation is a thin slot dug perpendicular to the trench. This is where your line will sit. The goal is to avoid any upward pressure on the line, so the slot should start as deep as the trench and gradually get shallower as it moves away from the trench.
Here's a great video from teamBMC that shows how to build a T-slot anchor using skiing gear. The same technique could easily be applied to sand or loose dirt, using a log or other long object as the anchor device.