What does the earth
consists of?

Above the core is Earth's mantle, which is made up of rock containing silicon, iron, magnesium, aluminum, oxygen and other minerals. The rocky surface layer of Earth, called the crust, is made up of mostly oxygen, silicon,aluminum, iron, calcium, sodium, potassium and magnesium.

Earth's crust is made up of several elements: oxygen, 47 percent; silicon, 27 percent; aluminum, 8 percent; iron, 5 percent; calcium, 4 percent; magnesium, potassium and sodium, 2 percent. The crust is divided into huge plates that float on the mantle, the next layer.

Ba rock that formed 1,400 million years ago!

Why you put last one a? i think is b.