[Gmsh] 2D to 3D

[Hines, Albert M.]

Please pardon the lack of experience, but I have a closed triangulation
such as this:

		$MeshFormat
		2 0 8
		$EndMeshFormat
		$Nodes
		5
		1   0.0   0.0   0.0  
		2   1.0   0.0   0.0  
		3   0.5   1.0   0.0  
		4   0.5   0.6  0.75  
		5   0.5   0.1  0.75  
		$EndNodes
		$Elements
		6
		1 2 2 1 0   2 3 1                
		2 2 2 1 0   5 4 2                
		3 2 2 1 0   4 3 2                
		4 2 2 1 0   4 1 3                
		5 2 2 1 0   1 4 5                
		6 2 2 1 0   5 2 1                
		$EndElements

and simply wish to generate a conformal linear tetrahedral mesh.
However, when I attempt a 3D mesh, nothing happens. Do I need to
manually define some sort of volume to which these triangles belong?
Puzzled,

Albert Hines