You're dealing with the physics of the camera and you've discovered why most landscape shooters work in the early morning or late evening. During the day, unless special conditions exist, the light is just too harsh. You can still take pictures but they're going to fall into the "snapshot" category.
Problem #1
The human eye can detect and distinguish about 11 stops of information. The camera can see about 5 under normal conditions. When shooting RAW and employing some alternate processing you can push that to around 7 stops; still well short of what you can see with your eye. This is what happened on the second shot. You've got a scene with bright highlights and lots of shadow. The camera tried to expose for the shadows and the sky is about 8 stops brighter so it got blown out.
Problem #2
You're in full automatic mode. The light sensor in the camera believes that entire world is neutral grey. It looks at the area that you've set for metering (partial, spot, weighted, etc.) and determines what exposure would be necessary to make it grey. That works really well if your scene has lots of neutral tones or is evenly lit. In your 1st scene, the sky, which is generally pretty close to a neutral tone determined the exposure.
There are solutions to both scenarios. Key to all of that is learning to get the camera out of automatic and learning to read a histogram. Use the histogram, not the image on the screen, to determine if your exposure is good. If the histogram is off the screen on either end, you need to adjust the exposure. Don't assume that the camera knows best.
In a high dynamic range situation you have a few choices.
1. You can decide which is more important, shadow or highlight detail and expose for one or the other. In some cases, recomposing the shot can help take a problem area out of the shot.
2. You can "extend" the range of the sensor by employing
graduated neutral density filters. I use the crap out of these things. It allows you to darken a portion of the scene to bring the total range of tones down to the point that you can capture them all. The come is many different sizes and styles. Don't buy the screw in type. I just hand hold them in front of the lens.
3. You can take multiple exposures of the same scene and combine them manually or with a program like photomatix (HDR). Alternatively you can process the RAW file twice; once for the highlights, once for the shadows. Then you can blend the two frames in Photoshop.
Problem #3
The images aren't sharp. It's hard to tell if it's a focus problem, depth of field problem or motion problem but a good tripod will always improve your images.
Cheers
