55. columnar joints in a basaltic lava flow are produced by which process? a. compaction of the flow during burial b. compression-related warming and expansion of the flow c. contraction and tension during cooling of the flow d. none of the above

The hypothetical island country of gilder lies in the mediterranean sea off the coast of france. demographers have studied gilder for the past 50 years. at the beginning of the study, gilder had a population of 20 million. the demographers have measured birth and death numbers, as well as immigration and emigration numbers, as shown in the data table. from the data, calculate the population of gilder for each 10-year period by filling in the population (no) and population (nt) columns in the data table. use this formula to do your calculations: population size: nt = no + (b + i) – (d + e)initial population = 20,000,000