Ubucda dhulku, loo yaqaano (Earth's Core) waa bu'da ama lakabka dhexe ee meeraha dunida. Qaybtani waa dareere aad u kulul oo leh qiyaastii qaro (thick) dhan 2,266 km (1,408 mi) taas oo kooban birta Aayron iyo Nikel. Ubucda dhulku waxay ka hooseysaa lakabka labaad ee mantleka. Bu'da dhulku waxay oogada sare ka hooseeysaa dherer dhan 2,890 km (1,800 mi) oo ah meesha Ubucda dhulku ka bilaabanto, ilaa 5,150 km (3,200 mi) oo ah badhtanka dhulka. Heerkulka ubucda dhulku waxa uu ka bilaabmaa 4400 °C (8000 °F) maqaarka ubucda ilaa 5,430 °C oo ah bu'da dhexe iyo meesha ugu kuleylka badan dhulka. Dhinaca kale, cadaadiska (pressure) Ubucda dhulku waa inta u dhexeeysa 330 ilaa 360 gigapascals (3,300,000 to 3,600,000 atm). Ubucda dhulku waxay ka samaysan tahay isku dhisyo badan oo u badan Nikel iyo Aayron. Sidoo kale, Dahab iyo Balatiiniyaam badan ayaa iyagana laga helaa badhtamaha dhulka. Guud ahaan, bu'da dhulka la'aanteed nolosha dunidu waxay noqon lahayd nooc kale, sababtoo ah lakabkani waa sal-dhiga magnetka (magnetic field) dhulka.