Tinder has a minimum age limit of 13

"Eligibility. No part of Tinder is directed to persons under the age of 13. You must be at least 13 years of age to access and use the Service. Any use of the Service is void where prohibited. By accessing and using the Service, you represent and warrant that you have the right, authority and capacity to enter into this Agreement and to abide by all of the terms and conditions of this Agreement. If you create an account, you represent and warrant that you have never been convicted of a felony and that you are not required to register as a sex offender with any government entity. Using the Service may be prohibited or restricted in certain countries. If you use the Service from outside of the United States, you are responsible for complying with the laws and regulations of the territory from which you access or use the Service."
Source:  Tinder terms & conditions, retrieved 4th November 2014
Note - You need to be on Facebook to sign up for Tinder, so this is simply Tinder's way of authenticating identity.