The Sierra Madre mountain range in the Philippines was formed as a result of tectonic activity along the Philippines Trench, a subduction zone located along the eastern coast of the Philippines. The mountain range was formed by the collision of the Philippine Sea Plate and the Eurasian Plate.  This collision is called the convergent boundary. 

In a subduction zone, one plate is forced under another, causing the Earth's crust to be uplifted and compressed. This compression and uplift creates a mountain range, such as the Sierra Madre, as the two plates collide and interact. The ongoing tectonic activity along the Philippines Trench continues to uplift and shape the Sierra Madre mountain range, which is now considered one of the most important and biologically diverse areas in the Philippines.

 The type of endogenic process that occurred in the Sierra Madre is diastrophism. This process occurred by mechanisms such as the lithospheric plate movement. It includes an orogenic process involving mountain building through severe folding affecting the earth's crust and along plate tectonics. The behaviors of the plates or rocks beneath the crust were also part of this process. 

This behavior is a type of continental-continental convergent, where two continental plates collide due to driving force. Continental lithosphere is low in density and very thick that's why it cannot subduct. So when two continental plates collide, they just smash together. This behavior is why the beautiful mountain range in the Philippines, the Sierra Madre, was formed. 

Rocks

The oldest rocks in Southern Sierra Madre comprise an incomplete ophiolitic sequence

called Angat Ophiolite. The ophiolitic sequence consists of layered and massive gabbro, pillow basalts, and turbiditic sedimentary rocks . 

• Gabbro- Gabbro is a coarse-grained (phaneritic), dark-colored (mafic), intrusive igneous rock. 

• Pillow Basalts- Pillow basalt is an extrusive igneous rock that forms when lava of basaltic (mafic) compositions erupts underwater, and it's a type of aphanitic textured rock.  

• Turbidite- A type of sedimentary rock composed of layered particles that grade upward from coarser to finer sizes and are thought to have originated from ancient turbidity currents in the oceans. 

Minerals

Mineral deposits, including copper, gold, chromite are believed to exist in abundance in the Sierra Madre mountain range in Luzon.

• Copper- Copper is a metallic mineral that is found in many minerals that occur in deposits large enough to mine. These include: azurite, malachite, chalcocite, chalcopyrite and bornite.  Most copper comes from chalcopyrite. 

• Gold- Gold is a metallic mineral as well. It is highly prized by people because of its attractive color, its rarity, resistance to tarnish, and its many special properties - some of which are unique to gold. 

• Chromite- Chromite is an oxide mineral composed of chromium, iron, and oxygen (FeCr2O4). It is dark gray to black in color with a metallic to submetallic luster and a high specific gravity.