How old is earth in Islam?
Is it age of earth in Islam near ~5000 years old or Islam shares scientific point of view of earth age?
According to Shia Islam the exact age of Earth is not mentioned but there are some Hadith that show the age of earth is millions or billions of years.
Firstly this verse of Quran is interpreted that humans lived before creation of Adam a.s. :
وَإِذْ قَالَ رَبُّكَ لِلْمَلَائِكَةِ إِنِّي جَاعِلٌ فِي الْأَرْضِ خَلِيفَةً ۖ قَالُوا أَتَجْعَلُ فِيهَا مَن يُفْسِدُ فِيهَا وَيَسْفِكُ الدِّمَاءَ وَنَحْنُ نُسَبِّحُ بِحَمْدِكَ وَنُقَدِّسُ لَكَ ۖ قَالَ إِنِّي أَعْلَمُ مَا لَا تَعْلَمُونَ
When your Lord said to the angels: 'I am placing on the earth a caliph,' they replied: 'Will You put there who corrupts and sheds blood, when we exalt Your praises and sanctify You?' He said: 'I know what you do not know'
Because this question of angels means that other humans lived before Adam a.s. on earth unless they did not asked such question.
In a Hadith Imam Sadiq a.s. said to one of his companions:
"لَعَلَّكَ تَرَى أَنَّ اللَّهَ عَزَّ وَ جَلَّ إِنَّمَا خَلَقَ هَذَا الْعَالَمَ الْوَاحِدَ وَ تَرَى أَنَّ اللَّهَ عَزَّ وَ جَلَّ لَمْ يَخْلُقْ بَشَراً غَيْرَكُمْ بَلْ وَ اللَّهِ لَقَدْ خَلَقَ اللَّهُ تَبَارَكَ وَ تَعَالَى أَلْفَ أَلْفِ عَالَمٍ وَ أَلْفَ أَلْفِ آدَمٍ أَنْتَ فِي آخِرِ تِلْكَ الْعَوَالِمِ وَ أُولَئِكَ الْآدَمِيِّين"
Perhaps you think Allah (AWJ) created only this universe and created no humans unless you?! Yes, By Allah Indeed God created thousands of thousands of universes and thousands of thousands of Adams that you are at the end of those universes and Adams.
Another hadith from Imam Baqir a.s. (the 5th Imam of Shia) sais:
لَقَدْ خَلَقَ اللَّهُ عَزَّ وَ جَلَّ فِي الْأَرْضِ مُنْذُ خَلَقَهَا سَبْعَةَ عَالَمِينَ لَيْسَ هُمْ مِنْ وُلْدِ آدَمَ خَلَقَهُمْ مِنْ أَدِيمِ الْأَرْضِ فَأَسْكَنَهُمْ فِيهَا وَاحِداً بَعْدَ وَاحِدٍ مَعَ عَالَمِهِ ثُمَّ خَلَقَ اللَّهُ عَزَّ وَ جَلَّ آدَمَ أَبَا الْبَشَر
Indeed Allah (AWJ) in this earth, from the time created it, created seven world that were not from children of Adam. created them from surface of earth. so God inhabited them on earth and made one generation after another generation and for each made a world after another world on earth until finally created Adam the father of Bashar* and divaricated his descendents from him.
Reference of hadith: Shia hadith book Bihar al-Anwar volume 54 page 320
Ineed Islam does not say earth is young or has small ages like 5000 or 1000. age of earth is not clearly mentioned as we know. InshaAllah Imam Mahdi a.s. comes soon and scientists can ask him.
Quran is somewhat a cryptographic book, too much data claimed to be stored therein within only the size of a usual book, say 500 pages. If you read Hadith from Ahlol-Bayt you will find many interesting points there in verses that you have already passed over them for times but never mentioned them. According to Quran itself:
That this is indeed a qur'an Most Honourable; In Book well encrypted and guarded; Which none shall touch but those who are clean; A Revelation from the Lord of the Worlds. (Al-Vaaghe'e:77,78,79,80)
That is, no one should touch its text but after getting clean (say, for Muslims by making Vozu') and its inside meaning by cleaning his/her hearth with the light of faith. Maybe someone would think about the days i the viewpoint of the creator, Allah, being different in different situations or for different creatures, for example Allah says:
The angels and the spirit ascend unto him in a Day the measure whereof is (as) fifty thousand years (Al-Ma'aarej:4)
then use the verse that Allah says he has created the universe in 6 days:
We created the heavens and the earth and all between them in Six Days, nor did any sense of weariness touch Us. (Ghaf:38)
to obtain a value of equal to 300,000 years for creating the Earth and the skies, not as for their age. Of course it is not acceptable in Islam that the Earth be 5000 years old when we believe Adam's descension occurred around 7000 years ago and many many Adams and their quite many children living here on earth before our parents being created from dust, however, I cannot as well support my above answer as if I am right according to Shia Islam time can vary (not inverted though I guess!?) remarkably, something similar to relativity theory but I'm not sure for time to change only with speed, actually it may change with speed but of course it changes with other factors as well that my little knowledge has never touched them. I've only seen its evidences in Shia Ahadith.
You may be able to find some guides to answer in Ahadith.
There's no reason to disbelieve the accounts of the holy prophets (pbut) who Allah sent to this earth before Muhammad. However, sticking just to the Quran.
It is Allah who created the heavens and the earth and whatever is between them in six ayums (Qur'an, Surah 32:4)
We know Allah took six days to create the earth and the universe.
Allah created Adam, making him 60 cubits tall. When He created him, He said to him, "Go and greet that group of angels, and listen to their reply, for it will be your greeting and the greeting of your offspring." bukhari 4:543
We know too that Allah created Adam (pbuh), Allah's first prophet, which he sculpted out of clay and dirt (the origins of humanity) and whom he sent from heaven to earth around 6000 years ago. He was the first human to step foot on this universe.
Allah has chosen not to fully tell us what he did with the earth between when he created it, and when he sent humans 6000 years ago - We do not know if there were beasts before mankind, whether Allah created the earth with their bones or whether their claimed existence is a plot by non-believers.
Please have a look at http://www.turntoislam.com for an interesting discussion about whether or not creatures (like Dinosaurs) really existed.