The I-94 card will be taken from you upon departure from the U. S. and you will receive a new one upon your return. Remember, it is easiest to obtain a visa in your home country. This is done by filing an I-824 Request for Consulate Notification, which must be filed by Columbia University. Please contact the ISSO or the IAO for cost and details. AND you are traveling overseas for a short period of time and are worried that you will not have time to obtain a new visa, you may apply for a visa revalidation through the State Department in Washington D.C. approximately one and one half months in advance of your departure.
Detailed instructions are below.
D.C. Once a complete application has been made, it can take 8 or more weeks to receive a visa. Complete instructions on how to apply are available on the State Department Web site. Consult the Canadian Consulate General for visa regulations concerning your country before making travel arrangements. Tourists cards or visas may be required for travel to Mexico. However, we recommend you carry your passport and I-94 card when you travel any distance from home.