広がる
ひろがる · hirogaru · JLPT N3 · verb-godan
to spread
広 hiro = wide, as in 広い hiroi + -garu: to grow wide, to spread out
広がる is the intransitive partner of 広げる hirogeru. The -aru ending means it happens by itself: a rumour or a view spreads out. The -eru ending means someone does it: you spread out a map.