The Quran claims that mountains prevent the earth from shaking. But science as well as empirical evidence has found this to be untrue.
Surah 21:31 PICKTHAL: And We have placed in the earth firm hills lest it quake with them, and We have placed therein ravines as roads that haply they may find their way.
 Dan telah Kami jadikan di bumi ini gunung-gunung yang kokoh supaya bumi itu (tidak) guncang bersama mereka, dan telah Kami jadikan (pula) di bumi itu jalan-jalan yang luas, agar mereka mendapat petunjuk.
Al-Baidawi explains “when the mountains were created on its (the earth’s) surface, and they centred it, thus serving as wedges to keep it from moving.
Muslim geologist, Dr. E. L. Naggar says, in his “The Geological Concept of Mountains in the Qur’an”, International Institute of Islamic Thought, International Graphics Printing Services (301 779 7774), 1981. “Continental orogenic belts are the result of plate boundary interaction, and such interaction reaches its climax when two continents come into collision. This results in considerable crumpling of the margins of the two continents and the cessation of all forms of activity at that junction. The two lithospheric plates become welded together, with considerable crustal shortening in the form of giant thrusts and infrastructural nappes, as well as considerable crustal thickening in the form of deep roots that extend downwardly for several times the elevation of the mountainous chain. Consequently, these collosal chains with their very deep roots stabilize the Earth’s lithosphere as plate motions are almost completely halted at their place. Again, the notion of a plastic asthenosphere makes it possible to understand why the continents are elevated above the oceanic basins, and why the crust beneath them is much thicker than it is beneath the oceans. This implies that inasmuch as mountains have very deep roots, all elevated regions such as plateaus and continents must have corresponding roots extending for an exceptional distance downward in the asthenosphere. In other words, the entire lithosphere is floating above the plastic or semi-plastic asthenosphere, and its elevated structures are only held steadily by their downwardly plunging roots
While this Muslim geologist holds the view that mountains keep the earth from shaking, this is not borne by scientific evidence. Professor of Geology, Dr. David A. Young says, “While it is true that many mountain ranges are composed of folded rocks it is not true that the folds render the crust stable.”
So what we have here is conflict opinions between the Muslim geologist and Professor Young. Who should we believe in? We should see what the evidence points to rather than just accept the opinions of experts that may be contradictory.
The fact is that mountains do not prevent the earth from shaking. Evidence shows that there are numerous earthquakes in mountainous regions. If mountains prevent the earth from shaking, how can this be so? Let’s refer to objective reports from encyclopedias.
Andes Mountains are the world’s longest chain of mountains above sea level. They stretch along the entire west coast of South America from Cape Horn to Panama for a distance of 7,200 kilometres. Earthquakes are common in the Andes. Many towns have been wiped out by them. Cities that have been greatly damaged by earthquakes include Valparaiso, Lima, Callao, and Quito. (Source: World Book)
The mountains of the Tethyan System consist largely of highly deformed sedimentary and igneous rocks that have been folded and faulted within the past 80 million years. Earth scientists consider the system to be a result of the African, Arabian, and Indian plates colliding into the Eurasian Plate. Earthquakes occur frequently along the Tethyan System, indicating that mountain building is still taking place. (Source: World Book)
Most earthquakes take place on one of two great earthquake belts that girdle the world. The belts coincide with the more recently formed mountain ranges and with belts of volcanic activity. One earthquake belt circles the Pacific Ocean along the mountainous west coasts of North and South America and runs through the island areas of Asia. It is estimated that 80 percent of the energy presently released in earthquakes comes from this belt. (Source: Compton Encyclopedia)
Some Muslim apologists realize that this statement contradicts science and have also tried to explain that the description of the mountains preventing the earth from moving is metaphorical.
If we look at the other instances of this verse in the Quran, we know that this cannot be true. For example in Surah 13:2-3, the same description of the earth and mountains are given together with a list of other things that Allah has created. Clearly it is meant to be interpreted literally and not metaphorically.
PICKTHAL: Allah it is Who raised up the heavens without visible supports, then mounted the Throne, and compelled the sun and the moon to be of service, each runneth unto an appointed term; He ordereth the course; He detaileth the revelations, that haply ye may be certain of the meeting with your Lord.
And He it is Who spread out the earth and placed therein firm hills and flowing streams…
Surah 13  Allah-lah Yang meninggikan langit tanpa tiang (sebagaimana) yang kamu lihat, kemudian Dia bersemayam di atas Arasy, dan menundukkan matahari dan bulan. Masing-masing beredar hingga waktu yang ditentukan. Allah mengatur urusan (makhluk-Nya), menjelaskan tanda-tanda (kebesaran-Nya), supaya kamu meyakini pertemuan (mu) dengan Tuhanmu.
 Dan Dia-lah Tuhan yang membentangkan bumi dan menjadikan gunung-gunung dan sungai-sungai padanya.
Other Muslims have said that the word for “shaking” used in the verses here is “tameeda” and not the Arabic word “zalzala”.
It is true that there is another word for shaking in Arabic, which is “zalzala”. However, there is no doubt that the word “tameeda” also has the meaning of shaking or quaking as it has been translated that way by all major Quranic translations.
YUSUFALI: And We have set on the earth mountains standing firm, lest it should shake with them, and We have made therein broad highways (between mountains) for them to pass through: that they may receive Guidance.
PICKTHAL: And We have placed in the earth firm hills lest it quake with them, and We have placed therein ravines as roads that haply they may find their way.
SHAKIR: And We have made great mountains in the earth lest it might be convulsed with them, and We have made in it wide ways that they may follow a right direction.