Gilbert Hill: A Lava Wonder


One of the greatest geological wonders of India, is hard to find. You have to make your way through grubby slums, high rises and crowded roads and when you finally see it, Mumbai’s Gilbert hill can be disappointing . But even then, you can't help but be awed by the geological significance of this outcrop!


Gilbert Hill in Mumbai is one of the greatest geological wonders of India

Hidden in Mumbai’s suburb Andheri, Gilbert Hill is a 200 ft (61 m) monolith column of black basalt rock. It was formed when molten lava was squeezed out of the Earth's clefts during the Mesozoic Era about 65 million years ago and the basalt found around the area are of volcanic origin.

In fact the entire Deccan plateau is a 5,00,000 sq. km slab of cooled magma which emerged from the volcano off the coast of present day Seychelles. Lava oozed out of Earth’s crust gradually for 4 million years flowing very slowly, sideways. And when it cooled and solidified, the Deccan plateau was formed before the Indian subcontinent moved and joined up with Asia in the Gondwana Age.


Gilbert Hill was formed during the Mesozoic Era about 65 million years ago

Gilbert Hill is a remnant of that volatile era and is a stand-out in many ways. Generally volcanic mountains are formed when lava rising to the surface, solidifies. With each subsequent eruption, the debris starts piling up higher and higher to form a mountain. However, sometimes lava behaves differently; it suddenly rises up vertically with great force between the traps (land slabs) in the earth forming a block. Such a form is called a laccolith.

The man who studied and codified this was none other than American geologist G K Gilbert, in whose honour the hill in Mumbai is named. Strangely, no records have come to light regarding when and why the hill was named after Gilbert. In 1952, Gilbert Hill was declared a monument of national importance by the Geological Survey of India to mark its historic significance.

Grove Karl Gilbert, the noted geologist after whom Gilbert Hill is named
Grove Karl Gilbert, the noted geologist after whom Gilbert Hill is named|Wikimedia Commons

The vertical columns of Gilbert Hill are similar to the Devils Tower National Monument in Wyoming and the Devils Postpile National Monument in eastern California, USA. Both these geological wonders in USA are well-protected and very popular tourist attractions where visitors come from near and far.



Devils Postpile National Monument in California, USA
Devils Postpile National Monument in California, USA|Wikimedia Commons

In stark contrast, slums and buildings have come up right next to Gilbert hill. In 2015, a local builder even attempted to break and destroy the hill using water jets! On top of the hill is a temple of Gaodevi, the guardian deity of the local village. It is the only thing that is protecting this great geological wonder from complete destruction!

Gilbert Hill in Andheri, Mumbai
Gilbert Hill in Andheri, Mumbai|Wikimedia Commons

Inputs from: Once Upon a Hill by Kalpesh Ratna


LHI TRAVEL GUIDE

Gilbert Hill is located in the bustling city of Mumbai, Maharashtra. The city has a well connected local and outstation railway network. Mumbai CST railway station is around 25 kms away and Dadar railway station is 14 kms away from Gilbert Hill. The nearest airport is Mumbai Chattrapati Shivaji International Airport about 5 kms away.

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