What is the difference between lava flow and a volcano?

Answer 1

When minerals (all sorts of rock) become so hot they glow red, and then get even hotter, they melt, just like ice melts to become water. This melted (or "molten", meaning it is still hot enough to be liquid, not hardened yet) rock has two names: if it is still deep underground, it is called "magma". When it comes out of the ground, or is very near the surface of the earth and might come out soon, people call it "lava."

So a "lava flow" is any stream or movement of molten rock, at or near the surface of the earth.

A volcano is a geologic structure formed by magma pushing up to the surface of the earth, like a planetary pimple, and then bursting out either as lava or some other pyroclastic form: if a volcano is created, grown, or changed by a gentle eruption, you'll see a lot more "lava flows". If the volcanic eruption is explosive, the explosion will not "flow" at all, but burst like a bomb. Google "Mt. St. Helens eruption" or "Krakatoa explosion" for more about that. After the initial explosions are over, there may be calmer flows of lava before the magma pressure equalizes and the volcano settles down again.

By the way, a classic volcano is a cone-shaped mountain with a magma vent running up the inside of it. "Lava flows" can erupt out of any part of that volcanic cone: the lava, just like water under pressure in a cracked container, will follow any cracks or weak places it finds, it won't always bubble up out of the very top. Volcanoes come in many shapes, forms and sizes; so do lava flows. The two main kinds of lava flows are "pahoehoe" (fast-flowing lava that cools in ropy and swirly textures, and tends to flow AROUND buildings and trees and poles) and "a'ah" (slow-flowing lava that creeps along in a tall rough wall, which cools in very rough textures more like bristly crushed glass, and tends to bulldoze OVER buildings and trees and poles). These words are Hawaiian. I have no idea why they became the regular English words for these kinds of lava, except that they sound pretty cool, and the Hawaiians know about and care about lava flows a lot more than most other English speaking folks. And British & American geologists went to Hawaii to study vulcanism and lava in the 1800s. When they asked "what the heck is that?" the person answering the question was most likely to be a Hawaiian or someone who lived on those islands, so they would give the most specific name they knew-- the Hawaiian name!