Why Do Volcanoes Sometimes Explode and Sometimes Flow Quietly?

Sometimes, a volcano acts like it's angry and explodes; other times, it just calmly flows out. Think of it like this: if the lava inside is thick and sticky, it doesn’t want to come out fast, so it oozes slowly. But if the lava is runny and full of gas, it builds up pressure until boom! it explodes. The difference comes from what kind of lava the volcano has.