Week 7 Death Valley

The photo I chose of Zabriskie Point shows massive dunes within the desert habitat. A lake is visible in the distance and caught my eye. My thoughts wandered towards the cause of this lake to subside and water to be present only in that area? Why are the dunes jagged and sharp in their definition? Did water form the dunes that are seen in the picture? Or was something else responsible? A geological map would help me to decipher if the sand present was made of the same material as that found in lakebeds within the area.