While exploring a dormant volcano I noticed a pattern in the size of the pebbles. Lapilli, also known as “little stone,” had a consistency of being closer to the volcano. The size of lapilli is about 2mm to 64mm.When further away the pebbles get smaller and smaller until you have volcanic ash, which is considered anything smaller than 2mm. A volcanic bomb is really close to the volcano. These are anything bigger than 64mm. If you were taking notes those would be the observations you see and lapilli would come later.
There are many ways you can tell if you are near a crater, one way I will explain is looking at the size of the pebbles. When there is an eruption, debris emits from the volcano. Debris such as magma comes out and it hardens in the sky. When little pieces harden they travel further than the heavier pieces. The volcanic ash, which is smaller than 2mm in diameter, travels further than the volcanic bombs and lapilli, which are bigger in diameter. So if you’re walking toward a volcano and your taking notes you will notice that in the beginning the rocks are smaller and called volcanic ash. Scientists say that volcanic ash can travel for miles. If there is to much it can block the suns rays and cause global cooling and ice ages. Volcanic ash makes up most of the pyroclastic material you see in the volcanoes. As you walk they will get bigger and turn to lapilli. As you get really close to the crater there will then be volcanic bombs on the ground. This is how you know how close you are to a volcano that may have once erupted.
There are many ways you can tell if you are near a volcano. I have described one of the most common ways to tell. First it will start as volcanic ash when you are far away. Then, it will turn into larger material called lapilli. When you get really close the biggest of volcanic rocks, volcanic bombs, are what you will see. This is how you can tell if you are walking towards the center of a volcano, or going away. JL5