The Municipality of Calaca, Batangas is located at 13° 56` latitude and 120° 49` longitude at the southwestern mouth of Luzon Island along the western part of Batangas Province. It is situated East of the Municipalities of Balayan, Tuy and Nasugbu, west of the Municipalities of Lemery and Laurel and North of Balayan Bay. It lies within the southwest slopes of the Talisay. Calaca is a coastal town, being bounded by Balayan Bay on the South. It is a plain near the shore, gently rolling in the middle and going steep o the northern-most part adjacent to Gulod ng Batulao.
Geology and Geomorphology
Calaca has total land area of 11,270.943 hectares. Tephra deposits of calderas, maars, tuff rings and cones including large-scale surge deposits led to the formation of Calaca. The process is called volcanism, upon the formation of the Taal Volcano Calderas some 140,000 years ago. Mt. Batulao located at the northwestern tip of Calaca, then was a volcano and acted as a barrier in such a way that it blocked pyroclastic materials coming from erupting Taal Volcano.
Pyroclastic materials are ejecta consisting of unconsolidated materials of different sizes that are explosively or aerially deposited from volcanic vents. The upland portion of Calaca came from pyroclastic materials due to continuous base surges from series of volcanic eruption of Taal Volcano.
The low land area is classified as volcanic tuff that was formed mainly due to ash fall and continued lahar flow. Volcanic tuffs are ejecta from Taal volcano and formed underwater resulting to consolidation.
The coastal area came from weathered materials due to rain and sedimentation, thus giving birth to alluvial soil. Alluvial soil consist of fluvialite segments of unsorted and unconsolidated clay, silt, sand, and gravel reworked pyroclastic and volcanic rock segment. (PHILVOLCS)
It can be concluded therefore, that the upland area of Calaca is composed mostly of igneous materials and the lowland area of sediment origin carried in the coastal area by water and wind actions. Continuous based surges from pass eruption of Taal Volcano made the slope of Calaca in the upland area very steep. The areas along river channels as well as their tributaries have steep slopes, since the soil is loosely consolidated and easily eroded, Generally, Calaca has a terrain described as a highly dissected due to the presence of several sub-parallel streams or barrancas.
Topography, Slope Aspect and Elevation
The Municipality is divided into three ecosystems. The coastal ecosystem generally has a lope level of 0-3%. The following Barangay fall under this ecosystem: Dacanlao, San Rafael, Quizumbing, Camastilisan, Lumbang Calzada, Salong, Talisay, Puting Bato East, and Puting Bato West.
The Lowland ecosystem generally has a slope level of 3-8%. The Barangay under this ecosystem are Barangays 1-6, Bagong Tubig, Puting Kahoy, Lumbang na Bata, Pantay Madalunot and Timbain, Coral ni Lopez, Loma, Portion of Dila, Coral ni Bacal, Lumbang na Matanda and Calantas.
The upland Barangays generally has a slope level of 18% to 50%. These Barangays are Taklang Anak, Balimbing, Matipok, Niyugan, Caluangan, Dila, Munting Coral, Makina, Cahil, Bisaya, Bambang, Baclas and Tamayo.
The Highest elevation in Calaca is located in Barangay Cahil with an elevation of 613m above sea level.
There are two soil types that can be found in Calaca, namely:
Taal loam which is located in the northern portion of the municipality covering an area of 7,889.66 hectares. This soil type came from weather materials from pass-based surges of pass eruption of Taal Volcano. It is generally grayish brown to light gray when dry and dark brown when wet. This type of soil should have limited cultivation and requires very careful and land management;
Taal Sandy loam on the other hand can be found in the southern portion of the municipality, and covers an area of 3,381.28 hectares. This soil requires careful land management.
The Physiography of Calaca is of three types: Scarpment, Broad Alluvial Plains, Volcanic Hills and Mountain. The coastal ecosystem of Calaca is located along the broad alluvial plains. The lowland ecosystem is located mainly along broad alluvial plain while some portions are along volcanic hills. Majority of the upland ecosystem, lies along volcanic hills and some belong to the mountain type, Scrapments are present in all three ecosystem except within Barangays 1-6.
Permeability is the property of soil to allow air and water to move into the soil layers.
The coastal ecosystem that is 1 km away from the coastline has moderately slow permeability. This is due to slope level of 0-3% and its soil type, which is mostly sandy I nature. Water from the uplands generally retains in this area therefore making it flood prone.
The lowland ecosystem, which has a slope level of 3-8% and a soil type of Taal loam has moderate to moderately rapid permeability.
Infiltration is the rate at which water enter the soil under the saturated conditions. It is reliable guide for the frequency and type of irrigation suitable for a given soil type. It gives an idea about the run off which is directly related to soil erosion.
The coastal ecosystem has a moderately slow to very rapid infiltration rate. the lowland has a slow to moderately slow infiltration rate and the upland ecosystem has a moderate to rapid infiltration rate.
Drainage, Tributary Patterns and Catchment Areas
Calaca has four major tributary rivers, namely: Dacanlao river, Bolbok River, Bagong Tubig River, and Cawong River. Rivers flow from the foothill of Mt. Batulao and drains into Balayan Bay.
Minerals Resources and Reserves
Sand deposits are found along riverbanks. Large scale quarrying is found in Barangay Dila resulting to sedimentation of the Sinisian River System. Quarrying in Dila is active and abandoned quarry sites were observed. The Sangguniang Bayan approved a municipal ordinance prohibiting such activity along riverbanks specifically those located near bridges along the national highway.