Roads basically function as thoroughfares. But there are some that go beyond this primary purpose and serve as a “classroom” for scientific learning.

Kennon Road – notorious for landslides and hairpin turns, and yet famous for stunning views of mountains and rivers – is one such example. The scenario begins when more than a 100 junior geology and mining students alight from scores of commuter vans and line themselves up along stretches of rocks and formations in the area. In this instant, open-air classrom, there are no seats, chalkboards or projectors, just a professor whose only prop is a megaphone. It is on him that all the attention is focused.

Dr. Mario Aurelio, professor at the National Institute of Geological Sciences (NIGS), U.P. Diliman, says: “Long before I became a geology professor, earlier generations of geology students had already been frequenting this road for their field laboratory activities.” These usually took place along the mountainside near Kilometer 229, where Aurelio says outcrops of alternating sandstones and shales, cut by andesitic dikes, are exposed.

But why Kennon Road?

For Aurelio, the road beside Bued River is an ideal destination due to its accessibility. But more importantly, Kennon Road, he explains, presents a stratigraphic (stratigraphy is the branch in geology that studies rock layers, or strata, and layering, or stratification) sequence – the succession of several rocks with distinct characteristics and known geologic ages – as well as stretches of outcrops that are very rare in navigable areas in a tropical country like ours, but which are necessary for a surface geological study to be possible.

Rolando Peña, author of Lexicon of Philippine Stratigraphy and consultant at the Geoscience Foundation, further emphasizes Kennon Road’s importance, saying it cuts across the beddings or direction of the length of these layers, exposing their cross-section. “When one travels down from Baguio City, from Camp 6 to Camp 1, the stratified rocks are traversed from oldest to youngest – from the Pugo Formation to the Zigzag Formation to the Kennon Limestone to the Klondyke Formation.

“Here and there, igneous rocks intrude into these stratified rocks, so you almost get the whole package of rocks in Baguio City just by traversing Kennon Road. Nowhere else is there such variety in types of rocks that constitute the Baguio District as in Kennon Road–Bued River.”

Geology students from other schools like the Mapua Institute of Technology and Adamson University also do their field studies along Kennon Road. Aurelio, who completed his postgraduate studies in the fields of structural geology, tectonics, geodynamics of oceans and continents at the Université Pierre et Marie Curie in Paris, says: “The varied rocks exposed along Kennon Road and Bued River, some mineralized with gold and copper, are not only useful in to students of Structural Geology, but also ideal field laboratories for studies in stratigraphy, paleontology, ore deposits and slope instability hazards, among others.”

The succession of rocks built up over millions of years are best exemplified by the rocks exposed along Kennon Road, according to Peña. These are the rock pile formations of the district. These stratified layers of rock formations on Kennon Road are represented by the Pugo Formation, Zigzag Formation and Klondyke Formation, which boast a combined thickness of more than 5,000 meters, a sizeable pile if laid out horizontally, layer by layer.

Kennon Road has eight Camps, numbered starting from the lowlands, as the construction of the road proceeded, and which also featured the workers’ settlement areas. “There are a total of eight camps: starting from the toll gate in Rosario where Camp 1, the lowest elevation segment, is located. Beside the view deck in Camp 7 stands the bust of Col. Lyman W.V. Kennon,” Aurelio says. (Lyman led the corps of engineers, which built the mountain highway linking La Union to Baguio.)

He also notes the eight important geological formations within Kennon Road’s eight Camps. For example, in Camp 1, the Pliocene (from 5.3 to 2.6 million years ago), the Amlang and Rosario Formations are exposed, while the late Miocene (10.4 to five million years ago, a time of global drying and cooling) to Pliocene Klondyke Formation are best observed along Camps 2 and 3. The impressive and popular Bridal Veil Falls is also carved out of conglomerate layers of the Klondyke Formation, and the early-to-middle Miocene (23 to 15 million years ago) Kennon Limestone crops out in Camp 3.

Peña points out that as one descends from the popular Lion’s Head, red and green beds of the Zigzag Formation can be seen, which contains lenses of limestone. These are intruded by the Black Mountain quartz diorite near the Old Toll Gate in Camp 6 with the calcareous portions of the Zigzag Formation becoming the focus of chemical reactions with fluids from the quartz diorite giving rise to gold and other metallic deposits.

This provided the ore for the now-abandoned Thanksgiving Mine in Baguio. Adjacent to it is the Black Mountain Mine which produced copper porphyry type ore until the early 1980s.

Construction of Benguet Road, which extends from the lowlands in Rosario, La Union, to Baguio City in the highlands, began in 1903 and started operating early 1905. It was later renamed after Col. Lyman Walter Kennon of the U.S. Army Corps of Engineers which was responsible for
the project.

But why was it built in the first place? Definitely not because of its geologic relevance. It had more to do with the need for a mountain retreat for the foreigners residing in Manila, who found the lowland temperatures oppressive.
Boasting a cool, if not chilly climate, and
an alpine landscape, Baguio was the ideal candidate. The downside was that it was far from Manila, and could be reached – during the American Occupation – by a 24-hour sea journey between the capital and San Fernando in La Union. In stormy weather, the trip could even take up to a week, not including the minimum of two days by horseback up the mountain.

Building a road was the only solution.

Filipinos and Americans were not the only ones involved in birthing Kennon Road. There were migrant workers, representing at least 40 different nationalities such as French and Japanese recruited in the middle of 1903 for a project regarded as one of the most expensive and most difficult engineering feats of its day. The project entailed not only laying down the road, but necessitated even setting off explosives near the mountainside and cliffs along the canyons.

Since that time, Kennon Road has undergone various reconstruction and improvement efforts. A major one was conducted on 1990, following the Luzon earthquake which severely damaged the road and led to its closure. It reopened in September of the same year. With a reputation for being landslide-prone, especially during the rainy season, Kennon Road continues to experience maintenance works of varying degrees.

Despite this, no one can dispute Kennon Road’s importance to the scientific community. As a most uncommon classroom, it is indeed a gift to geologists all over the country.