A viscous fluid that possesses a yield strength which must be exceeded before the fluid will flow. Most lava flows are examples of Bingham fluids. When an initial shear stress is applied to a fluid lava (e.g. by increasing the slope angle) it will not begin to flow immediately. The slope angle, and therefore shear stress, must be increased until the yield strength of the fluid is exceeded, after which flow will occur. This contrasts with a Newtonian fluid, which has zero yield strength and will flow on any slope.