The Seven Lakes of San Pablo ( fil, Pitong Lawa ng San Pablo) are seven

volcanic crater lake A volcanic crater lake is a lake in a crater that was formed by explosive activity or a collapse during a volcanic eruption. Formation Lakes in calderas fill large craters formed by the collapse of a volcano during an eruption. Lakes in maars ...

s scattered around the City of San Pablo, in the

province A province is almost always an administrative division within a country or sovereign state, state. The term derives from the ancient Roman ''Roman province, provincia'', which was the major territorial and administrative unit of the Roman Empire ...

Laguna Laguna (Italian and Spanish for lagoon) may refer to: People * Abe Laguna (born 1992), American DJ known as Ookay * Andrés Laguna (1499–1559), Spanish physician, pharmacologist, and botanist * Ana Laguna (born 1955), Spanish-Swedish ballet d ...

Philippines The Philippines (; fil, Pilipinas, links=no), officially the Republic of the Philippines ( fil, Republika ng Pilipinas, links=no), * bik, Republika kan Filipinas * ceb, Republika sa Pilipinas * cbk, República de Filipinas * hil, Republ ...

The Lakes

7260San Pablo City Barangays Landmarks 34

The seven lakes of the city are: * Lake Bunot * Lake Calibato, sometimes spelled as Lake Kalibato *The twin lakes of Yambo and Pandin * Lake Palakpakin, sometimes spelled as Lake Palacpaquin or Palacpaquen * Lake Muhikap, also known as Lake Mojicap or Lake Mohicap *

Lake Sampaloc Lake Sampaloc is a volcanic crater lake on the island of Luzon, Philippines. It is the largest of the Seven Lakes of San Pablo, Laguna. Nearly half of the lake's depth has a shallow depression at the bottom, indicating its volcanic origin. The la ...

, also spelled as Lake Sampalok, the largest of the seven lakes

Geology

The lakes are

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

s or low-profile

volcanic crater A volcanic crater is an approximately circular depression in the ground caused by Volcano, volcanic activity. It is typically a bowl-shaped feature containing one or more vents. During Types of volcanic eruptions, volcanic eruptions, molten magm ...

s located in the San Pablo Volcanic Field. They are among the 200 small monogenetic

volcano A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often found where tectonic plates are ...

es found along the Macolod Corridor, a

rift zone A rift zone is a feature of some volcanoes, especially shield volcanoes, in which a set of linear cracks (or rifts) develops in a volcanic edifice, typically forming into two or three well-defined regions along the flanks of the vent. Believed t ...

between

Mount Makiling Mount Makiling (also known as Mount Maquiling), is an inactive stratovolcano located in the provinces of Laguna and Batangas on the island of Luzon, Philippines. The mountain rises to an elevation of above mean sea level and is the highest fe ...

and

Mount Banahaw Mount Banahaw (; also spelled as Banahao and Banájao) is an active complex volcano on Luzon in the Philippines. The three-peaked volcano is located at the boundary of Laguna and Quezon provinces. It is the highest mountain in both provinces an ...

, which is part of the larger Southwestern Luzon

Volcanic Field A volcanic field is an area of Earth's crust that is prone to localized volcanic activity. The type and number of volcanoes required to be called a "field" is not well-defined. Volcanic fields usually consist of clusters of up to 100 volcanoes ...

. These craters are formed by

phreatomagmatic eruptions Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions conta ...

, an eruption where ground water comes in contact with hot

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...

pushing up near the Earth's surface.

Petrographic Analysis

In a recent rocks and sediment analysis or

petrographic Petrography is a branch of petrology that focuses on detailed descriptions of rocks. Someone who studies petrography is called a petrographer. The mineral content and the textural relationships within the rock are described in detail. The class ...

study on the lakes and adjoining rivers in San Pablo,

sulfate The sulfate or sulphate ion is a polyatomic anion with the empirical formula . Salts, acid derivatives, and peroxides of sulfate are widely used in industry. Sulfates occur widely in everyday life. Sulfates are salts of sulfuric acid and many ar ...

concentrations were considerably higher than the naturally occurring sulfates from volcanism. Samples were taken from other areas underlain with similar volcanic rocks from the old eruptions (e.g. Taal volcano) like

Indang Indang, officially the Municipality of Indang ( tgl, Bayan ng Indang), is a 1st class municipality in the province of Cavite, Philippines. According to the 2020 census, it has a population of 68,699 people. The municipality is situated in the c ...

, in the province of

Cavite Cavite, officially the Province of Cavite ( tl, Lalawigan ng Kabite; Chavacano: ''Provincia de Cavite''), is a province in the Philippines located in the Calabarzon region in Luzon. Located on the southern shores of Manila Bay and southwest ...

and the

La Mesa Watershed The La Mesa Watershed Reservation is a protected area that preserves the only major watershed in Metro Manila, Philippines. Also known as the Novaliches Watershed, it contains the last remaining rainforest of its size in Metro Manila surroun ...

, the water supply

reservoir A reservoir (; from French ''réservoir'' ) is an enlarged lake behind a dam. Such a dam may be either artificial, built to store fresh water or it may be a natural formation. Reservoirs can be created in a number of ways, including contro ...

for

Metropolitan Manila Metropolitan Manila (often shortened as Metro Manila; fil, Kalakhang Maynila), officially the National Capital Region (NCR; fil, link=no, Pambansang Punong Rehiyon), is the capital region, seat of government and one of three List of metrop ...

. The analyses indicated that the elevated level of sulfates were not related to volcanism but

anthropogenic Anthropogenic ("human" + "generating") is an adjective that may refer to: * Anthropogeny, the study of the origins of humanity Counterintuitively, anthropogenic may also refer to things that have been generated by humans, as follows: * Human im ...

or man-made, and among the causes are

sewage Sewage (or domestic sewage, domestic wastewater, municipal wastewater) is a type of wastewater that is produced by a community of people. It is typically transported through a sewer system. Sewage consists of wastewater discharged from residenc ...

fertilizers A fertilizer (American English) or fertiliser (British English; see spelling differences) is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from ...

herbicides Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

pesticides Pesticides are substances that are meant to control pests. This includes herbicide, insecticide, nematicide, molluscicide, piscicide, avicide, rodenticide, bactericide, insect repellent, animal repellent, microbicide, fungicide, and lampric ...

etc.

Hiking trails

In 2005, the

Rotary Club Rotary International is one of the largest service organizations in the world. Its stated mission is to "provide service to others, promote integrity, and advance world understanding, goodwill, and peace through hefellowship of business, profe ...

of San Pablo City held a ceremony that officially opened the hiking trails that connect the seven lakes of the city. The Rotarians were aiming for economic, environmental and health benefits of the trails to the community.

Conservation

The lakes are threatened by human intervention and exploitation, most especially Lake Sampaloc, which is located right in the center of San Pablo City. Several illegal settlements, illegal fish pens, commercial and business infrastructures on the shores have proliferated on some of the lakes causing increased pollution. Overuse of commercial fish feeds have resulted in high nitrogen levels and low dissolved oxygen that has led to

fish kill The term fish kill, known also as fish die-off, refers to a localized die-off of fish populations which may also be associated with more generalized mortality of aquatic life.University of Florida. Gainesville, FL (2005) ''Plant Management in Fl ...

s in the early and late 1990s. In January 2004, fish kills were observed in six of the seven lakes. Various ecological conservation efforts by both government and non-government organizations, like the '' Friends of the Seven Lakes Foundation'', had been implemented in recent years. One of these is the demolition of human-made structures along the lakes' shoreline.Friends of the Seven Lakes (2000-02-12)
"Yakap sa Lawa - First Lakes Summit"
. Friends of the Seven Lakes Foundation. Retrieved on 2009-04-30.

References

External links

Friends of the Seven Lakes Foundation

{{Calabarzon attractions Monogenetic volcanoes Maars of the Philippines Tourist attractions in Laguna (province)