Earth's continental crust is made of igneous, metamorphic, and sedimentary rocks and is composed of SIAL elements. The continental crust is made of various layers and has a density of 2.83 g/cm, while the oceanic crust is about 2.9 g/cm.
The ontientla crust has usual thickness of 40 km (25 miles) thick and floats or rests on upper mantel or i.e the asthenosphere. While other parts of it lies within the mantel the depth of the continental crust ranges to 100 km,
Gorges are narrow/skinny valleys between hills or mountains that often have a stream or river running through it. Waterfalls are rivers that stop and drop vertically into another body of water.
I am absolutely sure that <span>the percent of the Sahara Desert is covered by sand sheets and dunes is definitely 25 %. Even though it might seem weird, it is actually correct and here are the pic from artcicle about Sahara which will pose as a proof : ) Do hope it will help! </span>