2) features of the ocean floor; 3) the concept of sea-floor spreading; and. 4) the nature of the Earth's magnetic field and the fact that it has reversed its polarity many times in the past. The Earth's layers â The Earth is a layered planet consisting of crust, mantle and core (Fig. 1).
Run your sprinklers for 15 minutes. Use a ruler to measure the depth of water in each can. Add all the numbers, and then divide by the number of cans to find the average output. This average number is your sprinkler number. It is the average amount of water your sprinklers apply in 15 minutes.
So, how much is an inch of water a week? Experts say this amounts to roughly six gallons per square yard per week. One crude but easy way to figure out how long you need to water to get one inch a week: scatter five empty tuna cans or other containers throughout your lawn. Turn on your sprinkler system and let it run for 30 minutes.