Rocks beneath your feet

It is always interesting to know what actually lies deep beneath our feet. 
The surface layer is generally soil, which can be deposited or eroded from rocks, forming boulders, cobbles, gravels, sand ,silt and clay. The thickness can vary up to 70m depth (generally in Sarawak), depending on the terrain conditions.  
The rocks beneath the soils are related to the long Earth history and can be of various types and conditions, as shown in the the following pictures. The first two boxes of core samples were from Kuching-Serian area while the last two boxes were extracted from Sibu. 
Why they are different? You have to study geology to know what it is about. Collection of rock samples can become a hobby !