THIS IS A SCIENCE QUESTION BTW not sure what to put for subject science isnt an option but this is science lol All rivers have deltas; explain the process that forms these common landmasses..

The answer to the first one is barometer.

If a particular resource is not useful or needed then the price would be considerably low. once that resource is needed the price or value will raise depending on how useful or needed it is especially if the resource is low in quantity, the consumers would pay whatever they have to, to get that material.