This is a poem about immigrant identity, so it's no wonder that geography and geographic imagery play a pretty big part in it. If we're immigrants, we journey from one place to another. Chin's poem refers to various locations ranging from China to the U.S., and she uses geographic imagery to get at the complexity of her own culturally-split identity.
Line 8: The speaker refers to Angel Island in California here. Angel Island is the location of an immigration station that a lot of immigrants—especially those coming from Asia—passed through. Angel Island was her father's first stop in America.
Lines 26-29: There are references to two locations in these lines: Hong Kong and Piss River (a nickname for Rogue River), Oregon, where the speaker's family first settled in America. These two locations indicate what a huge geographic (and cultural) gulf the family crossed in coming to America.
Line 46: The speaker's use of geographic imagery here suggests how we can't escape our roots. If we're from the "east" and keep going "west," we'll end up right back in the east again. Also, "China," the country, is always there beneath the surface of the soil.
Lines 86-87: In these lines, the speaker imagines being swallowed up by a "chasm." A "chasm" is a hole in the earth or rock. So here, the speaker uses geographic imagery in imagining her own death. The "chasm" also refers to the gulf between her Chinese and American cultures.