  The Internet of Things, crowdsourcing, social media, public authorities, and
other sources generate bigger and bigger data sets. Big and open data offers
many benefits for emergency management, but also pose new challenges. This
chapter will review the sources of big data and their characteristics. We then
discuss potential benefits of big data for emergency management along with the
technological and societal challenges it poses. We review central technologies
for big-data storage and processing in general, before presenting the Spark
big-data engine in more detail. Finally, we review ethical and societal threats
that big data pose.
