During the sudden catastrophic events that have occurred in this last decade, social media have proven their importance in the creation and management of ad-hoc crisis communities. These platforms are increasingly used as complementary support tools for conventional crisis management teams. Recent disasters (e.g. Haiti, Australia, Japan, Mexico, etc.) have demonstrated their real potential in providing support to emergency operations for crisis management. However, several questions remain unanswered regarding the efficiency of their usage and especially their integration into the conventional information collection systems (technological sensors, cameras, SMS, etc.) usually used for crisis mapping. This paper aims to present multi-layer crisis mapping using a social media-based approach. We propose a generic step-by-step methodology as an integrated approach that connects a set of needs to a set of appropriate responses. The concept presented in this paper is the need/solution matrix, which plays a key role in the design of a multi-layer crisis map. The paper ends with an experiment with the well-known Twitter microblogging platform.