Which of the following is a major challenge to volcano preparedness?

Please help me

Which plains area lies in both the united states and canada? altiplano central canadian shield coastal plains great plains

What are the two causes of density in deep current waters? a. salinity (how much salt) of the water and high temperaturesb. salinity (how much salt) of the water and low temperatures c. oxygen content of the water and high temperatures. d. oxygen content of the water and low temperatures

Which set of terms best describes a community of miners who live out in the countryside of west virginia and use specialized geological equipment to analyze the composition of rock?