Volcano main vent definition​

main vent - this is the channel through which magma travels to reach the Earth's surface. secondary vent - some magma may escape through the side of the volcano, particularly if the main vent becomes blocked. crater - this is found at the top of the volcano, where the magma erupts from.

The main hole that magma escapes from.

Explanation:

There are multiple holes, or vents, from which magma can exit from in a volcano. The biggest one, usually at the top, which most of the magma comes out of, is called the "main vent".

to prevent people from getting the ebola virus, countries around the world paid to doctors develop a new vaccine. now that the vaccine has been made, doctors will need to experiment on a large number of people to find out if it works safely.

what is the greatest limitation that scientists are dealing with as they try to figure out how to experiment with the ebola vaccine?

meditation is a practice of sitting still and quiet for minutes or even hours. it has been practiced for thousands of years and is even a part of religious practices for some people. carefully controlled, repeated measurements of brain activity have shown that meditation does increase certain chemicals in the brain and even grows the part of the brain that people connect with their current surroundings and activities.

are claims about the effects of meditation most likely scientific or pseudoscientific?

not pseudoscientific, because people have made claims about it but scientific observations have not been made