Welcome to SDC.<br /><br />Basically, an object that size colliding with Earth, both Earth and the asteroid, meteor or whatever are moving. Earth moving at nearly 66,000 mph around the Sun, and the object may be moving at anywhere from 45,000 to 75,000 mph relative to the sun. An enormous amount of energy is released in such a collision. The amount of energy released is determined by the angle of the incoming asteroid. The object most likely never hits the ground but atmospheric friction and rapid decelleration compress it enough to cause it to explode as an airburst a few thousand feet above the ground.<br /><br />The mountain size meteor kicks up billions of tons of dust and debris. A cloud would probably form that would be composed of thick dust from the meteor or asteroid exploding in the atmosphere or when surviving peices hit the ground.<br /><br />The dust cloud spreads, generating a global cloud cover that partially blocks sunlight. Plants die, the animals that feed of the plants can no longer feed so they die, extinction. After perhaps a few decades, things begin to return to some sense of normalcy. But its too late for any creatures that go extinct.<br /><br />This all assumes that the dinosaurs died in a mass extinction caused by a meteor, asteroid or other object. The asteroid impact theory is basically theory but supported by evidence such as the chixalub crater. Did it cause the mass extinction of dinosaurs 65 million years ago?<br /><br />Theoretically it could, but we don't actually know. <div class="Discussion_UserSignature"> <p><strong>My borrowed quote for the time being:</strong></p><p><em>There are three kinds of people in life. Those who make it happen, those who watch it happen...and those who do not know what happened.</em></p> </div>