坠

Bottom earth radical — a mound of soil on the ground line, the indexing radical here. The combined ideograph reads transparently: something tumbling (队/falling-figure) down to the ground (土) = to plummet, to crash. Same earth family: 地 land, 坡 slope, 坑 pit, 塌 collapse. Often paired with 落 to give 坠落 'plunge / fall from a height.'

Top 队 supplies the sound — duì shifting to zhuì with consonant change. Originally 队 (traditional 隊) depicted a figure falling down a slope (the 阝-mound radical plus a falling person) — its older meaning was 'to fall,' which is exactly the sense preserved in 坠. Modern Mandarin reused 队 for 'team,' but the older 'fall' meaning lives on inside 坠.