We all know what a volcano is and the catastrophic consequences of its eruption. There are countless films about this topic, and in recent years, several eruptions have devastated thousands of homes. Lava consumes everything in its path, destroying entire habitats. We always associate it with a thick, red liquid that burns everything. But did you know that there are different types of lava?
Yes, that's right. Lava varies depending on its origin and the surface it leaves behind after cooling, a characteristic that makes it quite easy to determine its type. If you're curious about this topic, I recommend you keep reading. We'll explain what lava and lava flows are, and what the different types are.
What kind of liquid is lava?
Before discussing the different types of lava, let's first explain what this liquid is to better understand it. Lava is the mass, or magma, of molten rock that originates inside the Earth and reaches the surface through a volcano. Very broadly speaking, two types of lava can be distinguished:
- Lava from basic magma: It is the most abundant and contains silicates with high iron and magnesium content.
- Lava from acid magma: On the other hand, the silicates of this type of lava are rich in potassium and sodium.
When classifying different types of lava, it's usually done according to the lava flow. What is a lava flow? Well, it's the sheet of lava that flows across the Earth's surface after a volcanic eruption. When this happens, lava tubes or channels are formed, as the loss of heat from the ground and contact with the atmosphere cause these flows to solidify. With this knowledge, it's possible to create simulations that can predict the path lava flows will take today. This way, we can anticipate which regions will be affected and take timely measures.
Lava flows: Characteristics
As expected, the characteristics of lava flows are directly related to the properties of the lava itself. However, we can list three features that affect the speed of lava flows:
- The fluidity of lava
- Viscosity
- Properties related to the percentage of silica
The type of lava determines the flow patterns. More fluid lava tends to produce thin, extensive flows. Conversely, more viscous lava results in thicker, narrower flows. However, the speed of the flow depends not only on these factors but also on the volcano's eruptive force and the surrounding topography.
Lava flows typically descend in a straight line down the slope of a volcanic cone. Eruptions often occur not directly in the main crater, but rather along various fissures within the cone. This results in the formation of lava fields or mantles. It's important to note that multiple lava flows can occur during a single volcanic eruption; there isn't always just one.
What are the different types of lava?
As we mentioned earlier, lava types are differentiated by flow patterns and depend primarily on the shape they take. Let's look at them below.
pahoehoe lava flows
The term "pahoehoe" comes from Hawaiian and means "smooth." This type of lava is also known as ropy lava and is quite basic. It forms the ropy or pahoehoe flow. In this case, the surface usually has a folded, wavy, or smooth appearance, very similar to the shape of a rope, which gives it its name. This characteristic that distinguishes this type of lava flow is generated by the rapid movement of the lava beneath the Earth's crust.
lava flows aa
Again, the name for this type comes from Hawaiian and translates as "burning" or "rocky with rough lava." In this case, the lava is basaltic and gives rise to what we know as aa lava flows. This type, when it cools, develops a fragmented, loose, and rough surface. This characteristic is due to the fact that the surface lava cools only partially because the pressure causes it to lose gases very rapidly. Consequently, it fragments and deforms.
Generally, aa lava flows advance quite slowly. Their speed has been estimated to be between five and fifty meters per hour. What this type of lava has in common with pahoehoe lava is that it also originates from basic magmas with a certain degree of fluidity. It should be noted that the flows of both types often form networks of channels and tubes.
Block lava flows
Another type of lava is block lava. It is primarily characterized by originating from intermediate-acidic magmas. As for its flows, block lava creates a fragmented surface composed of several large, irregular blocks as it cools. The edges of these blocks are typically angular.
Padded lava flows
Finally, we must highlight pillow lava. This type of lava originates from mafic magma, although it has occasionally been found in intermediate-acidic magma. It solidifies upon contact with water, forming a flow with the shape of stacked, rounded pillows (hence its name). Pillow lava flows can be generated by the eruption of a submarine volcano or by lava flows from a terrestrial volcano that reach an aquatic environment, such as a river, lake, or the sea.
Now you know the different types of lava and their flows. I hope this information has been interesting for you.