Earth's internal heat comes from which of the following? select all that apply.
a. volcanoes
b. convection cells
c. radioactive elements
d. leftover heat from earth's formation

Dentify one advancement from the industrial revolution that had a significant impact on agriculture, and discuss the benefits this advancement had on the industry.

One of the brightest comets of the 20th century was comet hyakutake, which passed close to the sun in early 1996. the orbital period of this comet is estimated to be about 30,000 years. find the semi-major axis of this comet’s orbit. compare it to the average sun-pluto distance and to the distance to alpha centauri, the nearest star to the sun, which is 4.3 light-years distant.

If scientists only detect p waves in a certain layer of earths interior what does that tell us?