With the Midwest and Southwest incidents in the news recently, it got me to thinking I really don't understand the science of turbulence.

So when you're bopping along at 35,000 feet, and you suddenly drop, oh, 3000 feet, is that caused by the upper-level equivalent of a wind shear -- essentially, a downdraft of air that pushes the plane down at a greater force than the engines are propelling it forward?

Similarly, a sudden rise -- is that caused by a powerful updraft of air?

Or, am I completely missing it and some other force is at play?