These diagrams show the different types of Hawaiian style activity, and how they depend on the rate at which magma is supplied to the vent from the summit magma storage system. The top diagram shows the situation where the supply rate is high. By comparing the blue and yellow arrows you can see that the bubbles rise at a rate much slower than the magma flow velocity. Although they start to float upwards, they have not gotten far by the time the magma reaches the vent; the high number of gas bubbles drives high fountains, which in turn supply a high volume of lava leading to `a`a flows. The bottom diagram shows a much lower magma supply rate (but the same bubble-rise velocity), meaning that many of the bubbles are able to float up and escape prior to the magma's arrival at the vent. In this case a lava pond with little or no fountaining, and tube-fed pahoehoe flows are the result.