I am reading in Mark chapter 4:35-41.  This is the story of the big storm on the lake with Jesus sleeping and the disciples freaking out, then Jesus calms the storm.  Jesus is upset with them "Why are you afraid? Do you still have no faith?" Mark 4:40   I am a little confused with this. I understand we are not to worry because He is in control, but I thought we were to cast our cares upon Him (and the disciples did go to Jesus with their problems). It is just a question that has bothered me and when I read it again I decided I'd ask. 

There are a couple of things going on here.

Mark’s Gospel moves very fast, so at this point they had been with Jesus for a while, but the reality of who Jesus really was had not sunk in. The word for "afraid" from Mark 4:40 is a word that describes timidity or dread. In Revelation 21 it is used of Christians who give up under pressure (essentially they are considered cowards). It is when something so terrifying happens that you want to wet your pants and run away.
 
In Mark 4:41 when it says they were filled with "fear" it is the where we get our word "phobia" from.
 
Essentially, there is a great storm that is tossing their boat around like it is nothing and Jesus stands up with great authority and tells the storm to be quiet. There was something about how Jesus revealed Himself to them in this moment that they had not experienced before. They raise the question, "Who is this? That even the wind and the seas obey Him?" The implied answer is "He is the God who made it all."
 
Think about these people who had been taught about God their entire life, and now Jesus is standing in front of them revealing Himself by quelling a storm, that could wreck ocean liners, with a mere word. To have that type of power displayed makes you realize how powerful God actually is and it freaked them out, just like it would us. There is a natural awe and dread that comes along with actually seeing the power of God. Jesus' rebuke of them was more of a "don't you run away and hide, don't cower when I reveal myself." It gave them a stronger and healthier understanding of Him.
 
Secondly, Mark was writing his gospel to Romans, it is very action oriented, and Romans want to know "did Jesus get the job done." This story would have a huge impact on those facing persecution in the Roman church. As Walter Wessel noted, "It assured them that the strong Son of God would go with them into the storm of opposition and trial." Essentially, there was nothing to cower from because it all rests in Christ's capable hands.