What figurative language is in "Mom had grown up in the desert. She loved the dry, crackling heat" from page 21 of The Glass Castle? How do you know? What does this language tell you about the desert and Jeannette's mother?

The words "crackling heat" are an example of onomatopoeia. "Crackling" refers to the short, sharp sounds a fire makes when it's burning. Onomatopoeia is a word that describes or mimics the sound something makes. As a literary device, onomatopoeia is an effective means of making an author's prose more vivid.
In the book, the author uses onomatopoeia to highlight Jeannette's mother's love for the desert. "Crackling" describes the scorching desert heat perfectly. "Crackling" is also an emblem of Jeannette's mother's resourcefulness, tenacity, and fierce independence. From the text, we learn Jeannette's mother has the skills necessary to survive in the desert and thrive in her surroundings. Jeannette proclaims that her mother knows which plants are toxic and which are good for eating. Her mother also knows where to find water and how to make do with what she finds.
Jeannette maintains that her mother is courageous enough to drink unpurified water, as "long as animals were drinking from it." To make toothpaste, Jeannette's mother teaches her children to mix hydrogen peroxide with a little baking soda. In short, Jeannette's mother welcomes the "emptiness and severity" of the open desert. Her love of the "crackling heat" testifies to her courage, independence, and resourcefulness.