Why is the section stopping mid-page and continuing on the next column?

I’m running into a problem where the text will abruptly stop on the first column mid-page and move over onto the second column. I am using the TeXWorks editor and the TeXlive distribution with REVTeX 4.2 active. I’m wondering whether it has something to do with the use of REVTeX, but I’m not sure.

Here’s what I’ve compiled so far.

% For Phys. Rev. appearance, change preprint to twocolumn.
% Choose pra, prb, prc, prd, pre, prl, prstab, prstper, or rmp for journal
documentclass[aps,prl,twocolumn,groupedaddress]{revtex4-2}

begin{document}

%Title of paper
title{An agent-based mathematical model of optimal mine evacuation}

author{Tim}
%email[]{}
author{Bob}
%email[]{}
author{Jimmy}
%email[]{}

date{today}

begin{abstract}
noindent
Mines require fast but safe evacuation measures. We present a mathematical model that finds the optimal route to an exit that miners could use in the case of life-threatening hazard. Optimality is defined by how quickly the miner could use that path to get to an exit and how safe the path is. Once the mine is constructed, pathway blockages are added to emulate the event of a cave-in. We show that the model finds the optimal path for a given starting coordinate and that, in the case of a blockage obstructing the usual path, will reroute the miners to the second-most desirable.
end{abstract}

%keywords{}

maketitle

section{}
In the event of a mine evacuation, miners must be able to evacuate safely and efficiently. This need necessitates, then, that optimal evacuation procedures are determined for every mine. This paper will present an agent-based, mathematical model that will find the shortest possible path to an exit from a miner, for any given position. The model will not only consider the time to the exit but also the suitability of that path, e.g., there is a blockage on a path, not allowing the miner to go that way. It makes use of a graph approach, based on a previous model by Jalili and Noroozi (2009), and incorporates a path-finding function that calculates the shortest route between any number of exits. There are a few algorithms that can find the shortest path between any two vertices on a directed, weighted graph: Dijkstra’s algorithm; the Floyd-Warshall algorithm; and the Bellman-Ford algorithm just to name three. Previous models that use a graph approach to evacuation models have all used one of these or a combination of methods to get the same result. This model, though, was constructed in Mathematica, allowing for easier implementation of functions, and meant we could purely focus on its construction without worrying about the complex mathematics of graph theory. Each exit is represented by a vertex on the graph that corresponds to the adjacency matrix of the vertices and edges.

%subsection{}
%subsubsection{}
end{document}