Why silicon is abundant in earth surface?
Silicon, in the form of silica (oxidised silicon: Si4+ or SiO2), is indeed very common on Earth's surface.

This answer has two parts: why is silicon common in the Earth as a whole, and why it is concentrated particularly in the crust (therefore the surface).

Why is silicon common in the Earth

Silicon forms in nucleosynthesis processes in large stars (larger than our suns) and in supernovae. Turns out that quite a lot of silicon can be formed this way. When our solar system was still a hot molecular gas cloud, our region in place was rich in silicon (among other elements) so eventually Earth has lots of silicon in it. This is slightly beyond my field of expertise, so I will refer to the link daniel.neumann gave in his comment and to this good explanation at UCSB Science Line.

Why is silicon extremely rich in the Earth's crust?

Now we know there's quite a lot of silicon in the Earth to begin with. How do you end up with even more silicon in the crust (outermost layer) than in the mantle (middle layer, between the crust and the iron metallic core)?

The answer lies in what happens to rocks when they melt. You have a rocky mantle, with let's say 35% to 45% of SiO2. When this rock gets heated or decompressed (or wet, but nevermind this for now), it melts. But it doesn't melt completely, it melts only partially. This will always be richer in SiO2 than the original rock, and the residue of the melting now has even less SiO2. Once SiO2-rich melt moves upwards in the Earth (sometimes even erupting as volcanoes), it moves more SiO2-rich material to the crust. Over billions of year and large successive partial melting events, you end up having quite a lot of SiO2 in the crust.

This gets even better, because in those SiO2-rich rocks, you also have lots of quartz - which is a mineral composed of pure SiO2: 100% SiO2. This is a very resistant mineral to alteration and weathering. So if you have a granite that has only a third of quartz, with time the other two thirds (mostly feldspars) will decay and turn into clays (aka dust, mud). Only the quartz will be left behind, and the rest will wash away with water to the oceans (eventually). This is why you have impressive sand dunes which are "seas" of almost pure SiO2:



Some other questions on this website you might be interested in:

What was the likely composition of Earth&#39;s early crust (how did crustal composition evolve)?

Why do felsic materials have lower melting points than mafic?