 Ramba uchinyora ndima iyi - Portland iri pamusoro penzvimbo ine makomo anoputika inonzi Boring Lava Field, yakatumidzwa zita reguta riri pedyo reBoring. Boring Lava Field ine makoni esimbi anosvika 32 akadai seGomo reTabhori, uye muzinda wayo uri kumaodzanyemba kwakadziva kumabvazuva kwePortland. Mount St. Helens, gomo rinoputika zvikuru riri kuchamhembe kwakadziva kumabvazuva kweguta riri mudunhu reWashington, rinooneka nyore nyore pamazuva akajeka uye riri pedyo zvakakwana kuva rakasasa guta nemadota anoputika pashure pokuputika kwaro pana May 18, 1980.Matombo ari munharaunda yePortland ane makore akasiyana-siyana kubvira kumavambo kweEocene kusvika kumazuva achangopfuura. 