Other contributors have said "How was cinder cone formed?" is the same question as "How are cinder cone volcanoes formed?". If you believe that these are not asking the same thing and should be answered differently, click here.
How are cinder cone volcanoes formed?
Answer:
cinder cone volcanoes: consist of primarily erupted volcanic ash and rock fragments, or cinders. When the volcano erupts the ash and rock are ejected onto the mountain. As this process continues the volcano "grows" higher because of the debris build up.