Therefore，if the Earth began as a superheated sphere in space, all the rocks making up its crust may well have been igneous and thus the ancestors of all other rocks.
(独特构造may well have been――可能是)
主句：all the rocks may well have been igneous and thus the ancestors of all other rocks
从句1：if the Earth began as a superheated sphere in space
从句2：making up its crust
主句中2个宾语一部分igneous和the ancestors of all other rocks并排
名词性从句 主语从句 宾语从句 同位语从句
what VO=n. for eg
what SV=n. What you said is right.
形式宾语 Make it possible for sb.to do ?
That the ancestors of birds are dinosaurs is known.It is known that the ancestors of birds are dinosaurs.(形式主语占多数)
形式主语 It v (that SVO)=n.
强调句 It is/was A that B
并且一般状况下 It is/was……是强调句
The fact, that the ancestors of birds are dinosaurs, is known.
The fact, that the sun is round.
The book, that you bought for me. “that”当做宾语。