silica
caldera
viscous
denser
subduction
divergence
hot spots
earthquakes
Explosions from composite volcanoes occur as a result of gas buildup within them. Shield volcanoes also may erupt explosively if water accumulates inside their vents.
Answer:
Plate Tetonics
Explanation:
Plate interactions, as a result of plate tectonics, ultimately generate the various geologic settings where Earth materials can melt, metamorphose, and/or weather to become sediments.
If the coast-to-coast distance is about 2900 miles, it will take about ...
... (2900 mi)/(186000 mi/s) ≈ 15.6 ms
for the signal to travel coast-to-coast at light speed.
_____
There are time delays due to the amplifiers and repeaters required in the path, and due to the fact that the signals don't actually travel at the speed of light in a wire.
A test of internet speed between Seattle and Washington, DC shows a round-trip time of about 87 ms when traffic is light. Modern communication channels tend to be faster than the telegraph (especially when measured in words per minute).
