Danielle is writing an essay about Mount Everest. She includes the following:

In an average year, seven hundred to eight hundred climbers attempt the ascent to the summit. During peak climbing season, the mountain is often overcrowded with visitors, which makes climbing conditions less than ideal. Furthermore, climbers often line up in a tightly formed line, like sardines in a can, often tripping over one another's gear as they try to navigate their way to the top.

Her elaboration, in bold, is which type of elaborative technique?

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