The Chocolate Hills are one of the Philippines’ most unique geological formations, recognized worldwide for their symmetrical cone shapes and seasonal color changes. Numbering over 1200, they are not only a UNESCO heritage site but also a prime example of karst geology.
By visiting the site, you can learn how this extraordinary landscape was created. This EarthCache explores the karst geology of the Chocolate Hills, focusing on the processes of limestone weathering and erosion that shaped these remarkable features.
Formation of the Chocolate Hills
The Chocolate Hills are primarily made of limestone, formed millions of years ago when this region was submerged under a shallow sea. Over time, coral, shells, and marine sediments compacted into limestone. Tectonic uplift exposed this limestone to the surface, where weathering and erosion carved out the hills.
Key geological processes involved:
- Chemical Weathering: Rainwater, slightly acidic due to dissolved carbon dioxide, reacts with calcium carbonate (CaCO₃) in the limestone, slowly dissolving it and forming the characteristic karst landscape.
- Differential Erosion: Over thousands of years, harder limestone resisted erosion better than softer parts, creating the uniformly shaped hills.
- Karst Topography: The hills are part of a karst landscape, characterized by caves, sinkholes, and underground rivers, which further indicate the action of water on limestone.
- Environmental Impact: Seasonal changes influence the hills’ appearance, turning them brown during the dry season and lush green during the rainy season.
Tasks for the EarthCache
To log this EarthCache, complete the following tasks from the designated viewing platform:
1. Shape Observation:
Describe the shape of the Chocolate Hills. What do you think caused their uniform conical appearance?
2. Surface and Vegetation:
Observe the current color of the hills and describe the vegetation covering them. What environmental conditions might explain their color change between seasons?
3. Declaration of national geological monument:
Around the viewpoint, locate a black sign billboard with the title "Chocolate Hills National Geological Monument".
Look for the declaration of the National Comitee of Geological Sciences. Check the 3rd Paragraph, 2nd Line. What is the 3rd Word?
4. Geological Question:
Based on the description of karst geology, why is limestone particularly vulnerable to chemical weathering?
Logging Requirements
Send your answers to the tasks above to me via contact form or message center. Logs without submitted answers may be deleted.
Optional: Share a photo of yourself or a personal item at the viewing platform (no spoilers, please).
Additional Information
• Entrance fee: 100 PHP per person.
• A shuttle service is available from the parking area to the viewing platform.
• Please stay on designated paths and respect the protected status of the area.