Welcome onboard
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Turbulence is caused by sudden changes in wind direction and/or speed. If you imagine you're flying in smooth air then it suddenly changes direction, you'll feel a jolt as you cross the boundry. That's what caused it. The greater the change in direct or speed, the bigger the jolt. It's due to air masses moving around the atmosphere and also due to the land beneath, for example downstream of an area of mountainous terrain that causes the air to become turbulent as it passes over it. The easiest way to visualise what's happening it so look at a river. You'll find areas that are flowing constant and straight followed by areas that swirl and move in different directions and speeds. The turbulence is when you cross those boundries, it's the same fluid dynamics. You may find the following posts in relation to turbulence useful: Fear of Flying: Turbulence1 and Turbulence2 and Turbulence3.
I've flown to Turkey many times and apart from when crossing the Alps, where you get upwelling and turbulant air caused by the mountains below, flights are generally smooth. It ultimately depends on the current weather however. Depending on the exact routing, you'll generally only get a few small bumps for a short period, it's nothing major. You may not expereicne anything if the weather is smooth. You'll notice the cloud base outside increase when you're approaching the Alps then probably go through cloud. It's at this point you may experiences slight turlulence for 20 or so minutes until you pass through it and clear them. Other than that, I'm sure you'll have smooth flights so there's nothing to worry about.
Darren