What are warning signs of a volcanic eruption

Reading graphs: unemployment us unemployment rate (1961-2011) identify the trends in the graph and then use the drop- down menu to complete each statement from 1961 to 1965 unemployment was in the mid-2000s through 2011. unemployment was percentage unemployed 1961 1971 1981 1991 2001 2011 year

What first caused people to consider that the continents were once one large landmass?

As water is cooled from 4 c to 0 c its density