The long, narrow glaciers that form between mountains and are common in the Alps and Andes are called valley glaciers.

Here's why:

* Location: They form in valleys between mountain ranges, where they flow downwards due to gravity.

* Shape: They are typically long and narrow, with a distinct flow pattern.

* Examples: Famous examples include the Aletsch Glacier in the Swiss Alps and the Perito Moreno Glacier in the Andes.

Other types of glaciers exist, but valley glaciers are the most common type found in mountainous regions like the Alps and Andes.