Geography and Geology of the island of Java

Geography

Neighboring Java to Sumatra to the west, in eastern Bali, Kalimantan in the north, and

Christmas Island in the south. Java is the 13th largest island in the world. Waters surrounding this island is the Java Sea in the north, the Sunda Strait in the west, the Indian Ocean in the south, as well as Bali and Madura Strait in the east.

Java has an area of about 139,000 km2. The longest river is the Bengawan Solo, which is along the 600 km. The river rises in central Java, precisely in the volcano Lawu. The flow of the river then flows to the north and east, towards its mouth in the Java Sea near the city of Surabaya.

Almost the entire Java never gained the impact of volcanic activity. There are thirty-eight mountains that stretches from east to west of the island, all of which at a certain time once the active volcano. The highest volcano in Java is Mount Semeru (3,676 m), while the most active volcano in Java and even in Indonesia is Mount Merapi (2,968 m) and kelud mountain (1,731 m). Mountains and plateaus within remote help inland region is divided into several areas that are relatively isolated and suitable for wetland rice fields. Rice paddy fields in Java is one of the most fertile in the world. Java is the first place of coffee cultivation in Indonesia, namely since 1699. Now, many arabica coffee is grown in the highlands of Ijen either by small farmers as well as by plantations large.

Highlands Parahyangan, seen from Bogor (c. 1865-1872).

The average temperature all year is between 22 ° C to 29 ° C, with an average humidity of 75%. North Beach area is usually hotter, with an average of 34 ° C during the day in the dry season. South Beach area is generally cooler than the north coast, and the inland plateau area cooler again. The rainy season begins in October and ends in April, where the rain typically falls in the afternoon, and in the months of rain in others usually only intermittent course. The highest rainfall generally occur in the months of January and February.

West Java rainfall is higher than East Java, and the mountainous areas receive higher rainfall. Rainfall in the Highlands Parahyangan in West Java reached more than 4,000 mm per year, while on the north coast of East Java is only 900 mm per year.

Geology 

The most complete descriptions of the geology Java disclosed in van Bemmelen (1949). As an island, Java is relatively young geologically. Formation begins from the Tertiary period. Previously, the crust that forms the island is below sea level. Activities orogenis intensive since the Oligocene and Miocene epoch raised seabed so that the Pliocene and Pleistocene epoch form of Java has begun to form. The remains of the sea floor is still visible, forming most of the features of karst areas in the south of the island.

Van Bemmelen divides the island of Java in the following seven physiographic units.

South Mountains, is a zone of limestone mixed with the rest of the time Miocene volcanic activity are experiencing some of the appointment to the Quaternary period.

Volcanic Zone of the Quaternary period, with volcanoes, often with peaks above 2000 m above sea level, stretches from west to east butts.

Central depression, forming a basin axis as the main axis of the island, with two major depression: depression depression Bandung and Solo

Central anticlinal zone, consisting of deposits when Miocene to Pleistocene, starting from the Mount Reef continue east through Bogor, Serayu valley, then Kendeng Mountains, all the way to the northern coast Besuki.

Depression Randublatung, a small depression in the northern elongated Kendeng Mountains, formed from marine and terrestrial sediments.

Antiklinorium Apex-Madura, the formation of limestone hills on the northern coast of East Java and forming almost all parts of the island of Madura

Northern coastal alluvial plains (the northern Gaza) are formed from the delta and silt, is the youngest land.